System for executing first and second independently executable programs until each program relinquishes control or encounters real time interrupts5680645Abstract In an interactive network board, method and apparatus for multi-tasking independently executable programs, makes use of a ROM, disposed on the board, for storing (i) a monitor program, and (ii) first and second independently executable programs. The first and second programs each include a relinquish command. A processor is disposed on the board for downloading the monitor program and the first and second programs from the ROM to a RAM. The processor executes the first program in RAM until the first program relinquishes control. The monitor program then begins execution and stores in the RAM information which indicates the execution state of the first program. The second program then begins execution in RAM until the second program relinquishes control. The monitor program then recommences execution to store in the RAM information which indicates the execution state of the second program. Thereafter, the monitor program recommences execution of the first program, preferably from the point at which the first program relinquished control. Claims What is claimed is: Description BACKGROUND OF THE INVENTION
TABLE 1
______________________________________
Function Implementation
Notes
______________________________________
Network Controller
National DP 83902
With DP8392 COax
(206) Transceiver
Ethernet Interfaces:
10Base-2 (202)
Coax connector
10Base-T (204)
RJ45 connector
10Base-5 (203)
DB15 connector
(AUI)
Embedded Processor
NEC V53 16-bit/16Mhz MPU
(216) with DMA, timers,
Interrupts
EPROM (Flash) 256K Bytes Network program
(222) code, board BIOS
(Basic Input
Output Subsystem),
diagnostics
NVRAM 256 Bytes Printer
(220) Installation
Configuration on
Network
DRAM 512K Bytes Code execution and
(22) data buffering for
exp.port
SRAM 8K Bytes Buffering of
(214) incoming Ethernet
packets
SCSI Controller
NCR 53C90A 30-pin, internal
(224) I/F configuration
with power
MAC Address and
32 Bytes Stores MAC address
Hardware ID PROM and Hardward ID
(232) information
Board Size 100 mm .times. 125 mm
Type 2 EXP-I/F
PCB, double-sided
SMT
Power 5vdc, 710 ma DC converter on
board for Ethernet
+12vdc/-9vdc
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Preferably, the NEB 2 is installed inside the printer 4 in an expansion or options slot. The NEB 2 is thus an embedded network node with the processing and data storage features described above. The microprocessor 216 implements a data link layer of network packet transmission and reception. Network data transfer overhead is minimized through the use of a dedicated static RAM packet buffer 214 managed directly by the network controller 206. The microprocessor 216 accesses blocks of SRAM packet data and network messages through the network controller 206, and moves them into the large DRAM memory 220. Blocks of print image data and control information are assembled by the microprocessor 216 for transmission to the printer 4 by the SCSI controller 224 using the SCSI transfer protocol of the printer expansion port. Likewise, printer status information is transferred from printer 4 back to the NEB 2 in SCSI block format. The SCSI controller 224 operates concurrently with the network controller 206 for increased data throughput for overall NEB performance. The microprocessor 216 is preferably an NEC V53 chip which is a fast, highly-integrated microprocessor with a 16-bit Intel-compatible processor in support of Direct Memory Access ("DMA"), interrupt, timers and DRAM refresh control. Data bus structure on the NEB 2 is implemented 16-bits wide to take advantage of the 8-Bit/16-Bit dynamic bus sizing during microprocessor I/O transfers. Control firmware and printing application software for the microprocessor 216 are stored on the NEB 2 in EPROM 222. After power-on self-test, the firmware code is selectively moved to the higher-performance DRAM 220 for actual execution. Network and printer configuration parameters are written into NVRAM 228 when the printer is first installed onto the network. Thus, NVRAM 228 allows the NEB software to recover the installation parameters after printer power has been cycled off and on. 3. SOFTWARE Software for the LAN comprises a combination of network software, and NEB-customized software such as NEB-embedded software and software resident on the network administrator's PC. 3a. Network Software In the present embodiment, NetWare.RTM. network software is used to manage interactions between nodes of a network such that the client work stations can share and receive services from server nodes such as disk file servers, database servers, print servers, etc. NetWare.RTM. itself is a combination of software modules running on these server nodes and on each work station node. At least one file server may be provided in a Novell network. NetWare.RTM. runs as the operating system for the PC of the file server to provide basic network core services and utilities. File servers can connect to more than one LAN by using up to four network interface cards (preferably Ethernet or Token Ring connections). In these configurations, "bridging" or "backbone" services are provided between a plurality of LANs, as shown in FIG. 2, such that resources, including printers, can be shared "internet" i.e., from one LAN to another. On work stations, NetWare.RTM. runs in cooperation with the work station operating system (DOS or OS/2) as a NetWare.RTM. "shell" of control software. This shell has the effect of extending the services of the workstation operating system onto the network to make network resources appear local to the work station. Novell PSERVER software has the job of controlling a group of printers (up to sixteen) in order to service printing requests from network nodes. Requests are structured in a form of print queues that are held on the network file server using network queue management services. Queue entries contain a list of files to be printed. The files contain data to be printed such as tabs, formfeeds, and other Printer Description Language ("PDL") commands. Several queues can be serviced by a single PSERVER. Standard Novell servers are available in different versions depending on the type of network node they are to execute on. Print server programs can reside on the file server itself. A version of print server software may also be loaded on a stand-alone DOS station node to make that node a dedicated print server. By providing print server functionality (CPSERVER) to NEB 2 of the present invention, the NEB and attached printer will offer all the printing services of a standard Novell print server without the need for an attached PC. Printers themselves are considered to be either "local" or "remote". A local printer is one that is physically connected to the print server node. In the case of the NEB 2, the local printer is the printer housing the NEB. A remote printer is managed by RPRINTER programs running in the PCs they are connected to. RPRINTERs receive print data from PRINTSERVERS running elsewhere on the LAN. The NEB 2 of the present invention can be provided with RPRINTER functionality (CRPRINTER) to offer its printer as a network remote printer. In this mode, it is fully compatible with standard versions of Novell print servers. Novell NetWare.RTM. provides a number of print utilities to configure and control file server or work station-based print servers and their attached printers. The Novell program PCONSOLE is a menu-driven utility that allows a user (the printer console operator) to create a new print server, configure up to sixteen local or remote print ports, create print queues, assign queues to printers, and start/stop printer and server operations. 3b. NEB-Customized Software The NEB 2 is bundled with software modules that implement the full range of printing services offered by NetWare.RTM.. This includes external NetWare.RTM.-compatible modules that execute on work station nodes of the network in addition to internal NetWare.RTM.-compatible modules running on the NEB 2 inside the printer. The specific NetWare.RTM.-compatible programs developed for use with the NEB 2 (e.g., the customized CPSERVER and CRPRINTER programs to be discussed below) are provided with the same general operational interfaces as standard printing modules from Novell so as to be familiar to Novell users and network administration personnel. The customized versions include functional extensions that make use of the open architecture of the printer 4 to enhance print service management across the network. Table 2 shows the functions, implementations, and operational notes for the customized software developed for the NEB.
TABLE 2
______________________________________
Function Implementation
Notes
______________________________________
NEB-specific CPSERVER (92KB)
Customized Print
functions in NEB Server
EPROM CRPRINTER (40KB)
Customized Remote
Printer
NEB-to-Network
CPSOCKET (30KB)
Concurrent multi-
communication in protocol operation
NEB EPROM
NEB Environment in
(15KB) Monitor, loader,
NEB EPROM POST, etc.
Extensions to
CPCONSOL.EXE Remote Control &
NetWare .RTM.
(180KB) Stats, Auto-
PCONSOLE for Printer
CPINIT.EXE Reconfiguration,
Control/Configuration
(120KB) Print Job
in Administrator's Logs/Statistics
PC 14
______________________________________
3c. NEB-Embedded Software The software developed for the NEB 2 includes software embedded in the NEB and software loaded into the network administrator's PC 14. The NEB-embedded software provides both the NetWare.RTM.-compatible node and NetWare.RTM.-compatible print services directly inside the printer 4 without the overhead of a work station PC and its DOS operating system. The NEB-embedded software comprises a plurality of application modules (CPSERVER, CRPRINTER, etc.), real-time service modules, network protocol stacks, and a MONITOR program which performs application switching, process extension, device semaphores, and shares buffer-pool management. The functionality of the NEB is determined by the types of application modules and the number of protocol stacks of network layered communication software that are configured into the NEB 2. Interaction between the printer 4 and the network is coordinated by the MONITOR program which responds to real-time events while allocating NEB processing time to each application module on a multi-tasking basis. The NEB software functions at two layers: a "run-time" or real-time layer; and a "soft-time" or applications layer. The run-time layer is comprised of components of NEB software that respond to microprocessor interrupts. This layer services devices such as a timer, queued data transfer requests from the SCSI port, or LAN data through the protocol stack routine, and the CPSOCKET (to be discussed in section 4j below) communication mechanism. The soft-time layer is arbited and controlled by the MONITOR program (to be discussed in section 4l below) which gets control of the NEB microprocessor 216 after all real-time events have been serviced. A non-preemptive (cooperative multi-tasking) approach is used to divide the processor between the various application modules that are loaded such that no one application module can preempt other modules by capturing the microprocessor. The NEB EPROM 222 contains up to 256 KB of application module programs and NEB initialization code. At power-up or during a programmed reset, the NEB 2 executes a POST from the EPROM 222 before selectively transferring its EPROM code to NEB DRAM 220. If the POST is successful, the NEB 2 will load its protocol stacks and application modules into DRAM, and begin execution of its application modules. In its basic configuration, the NEB 2 contains NetWare.RTM.-compatible application modules comprising embedded versions of two configurations: the Customized Remote Printer ("CRPRINTER"); and the Customized Print Server ("CPSERVER"). Preferably, the NEB acts in only one of these configurations at a time. Further, these application modules require that a network protocol stack be loaded and functioning within the NEB. When configured with RPRINTER functionality, the NEB operates its printer as a slave to an external print server using a CRPRINTER module. In this configuration, the NEB exports to the LAN only limited printer status information in emulation of what the standard Novell print server expects from a standard Novell RPRINTER. However, extended status information about the printer will still be available if the CPCONSOL utility (discussed above) is executed in the network administrator's PC 14. As mentioned above, the NEB 2 includes embedded software programs CPSERVER and CRPRINTER which enable the NEB to act with either PSERVER or RPRINTER functionality on the network. The customized NEB-embedded software which permits peripheral status and control information over the LAN is CPSOCKET (to be discussed in section 4j below). CPSOCKET runs on the NEB and monitors the LAN for communications addressed to both the NEB 2 and the attached printer 4. Further, CPSOCKET communicates with CPINIT and CPCONSOL when they are running. CPSOCKET will maintain a table of default settings for the device environment, download basic configuration information (fonts and emulations) at power-up, provide device information, statistics, and log information for CPCONSOL displays, and provide reset, reboot, and download capabilities. CPSOCKET will also be responsible for the configuration of the NEB 2. Further, CPSOCKET will configure and activate applications on the NEB at the request of CPINIT. CPSOCKET also insures that the correct protocol stacks are available for each configured application. CPSOCKET will handle the settings of the NEB 2 and the printer variables at the request of both CPINIT and CPCONSOL. Finally, the download facility (e.g. the network administrator's PC 14) will contact CPSOCKET to carry out any firmware downloading, such as flashing EPROM 222, that is required. Upon initialization, programs such as CPINIT and CPCONSOL will issue a Service Advertising Protocol ("SAP") on the LAN looking for all network devices having the customized software of NEB 2. CPSOCKET will receive this broadcast signal and will respond. CPINIT or CPCONSOL then establishes a special connection with CPSOCKET using a customized client socket. CPSOCKET will then post multiple listens and will provide client service transactions such as NEB control, device information, basic configuration information, application information, statistics, and logging. For example, CPINIT can request that an application be configured, and CPCONSOL can request that an already-configured application be activated or deactivated. CPSOCKET will insure that the appropriate option (protocol stack) is available and configured for an application before allowing the application itself to be configured. Within the NEB, the CPSOCKET operational module is always activated. Additional print service applications may be utilized after loading further application modules into the NEB, for example, UNIX print services and associated protocol implementation. 3d. PC-Resident Customized Software To further enhance the functionality of the NEB 2, customized software is also provided to the network administrator's PC 14. For example, a Customized PCONSOLE ("CPCONSOL"; to be discussed in greater detail in section 4i below) utility provides extensions to Novell's PCONSOLE printer utility to enable access to the powerful control and monitoring features of the open-architecture printer 4. For example, the following are typical status control information available to the network from the printer through the use of CPCONSOL: (A) status and control information such as online/offline, no response, time/date/time zone, language, offsets, error skip settings, timer, buzzer enable, toner low, paper full, paper counter, count since last service, paper cut, paper jam; (B) font information such as primary, secondary, graphic set, scaling, rotation, elite; (C) layout information such as page orientation, line pitch, character pitch; (D) quality and common environment information such as number of copies, overlay, job complete, command mode, default paper size, current paper size; and (E) configuration information such as interface, buffer size, feeder select, duplex print, page stack order, etc. Furthermore, configuration data for the printer accessible to the network through the use of CPCONSOL includes: (A) network group information such as protocol type, the node name, the file server name, routing, POST error code, NEB firmware level, MAC address, server mode; and (B) printer group information such as safe (default) environment, font, disk present, disk size, initial environment, logging on/off, log file size, configured/nonconfigured, and net name. Additionally, logs can be kept of print job flow, print engine usage, and network behavior. Examples of such usage and statistical log entries include: (A) network group information such as receive statistics, transmit statistics, and non-media related information; (B) job entry information such as date/time/time zone, log-in (user's name), job name, pages, copy count, and print status; (C) initialization entry information; (D) error condition entry information; (E) clear log entry information; and (F) printer group information such as the number of jobs, pages/job, pages/minute, time/job, total pages/day, total jobs/day, number of days and total resets. CPCONSOL is a menu-driven DOS executable program whose function is to provide extensions to the Novell PCONSOLE printer utility. The CPCONSOL extension enables access to the additional control and monitoring features of the open-architecture printer 4. These features will enhance print service management across the network by allowing the network administrator's PC 14 to control and maintain the printer from a remote location. In summary, CPCONSOL is the utility that exports printer control features to the network administrator, allows reconfiguration of the safe (default) environment, and allows the network administrator to view network and printer status, job statistics, and a log of the previously-processed jobs and error conditions. CPCONSOL gathers the requested information by communicating with the NEB-embedded software program module CPSOCKET. Another customized software program resident on the network administrator's PC 14 is Customized Peripheral Initializer ("CPINIT"; to be discussed in section 4 h below) which is also a menu-driven DOS executable program. The function of the program is to configure, reconfigure, and initialize the printer 4 attached to the NEB 2. The CPINIT module will configure the NEB to act as a print server with one attached printer and specifies its primary file server by which the NEB will determine which queues to service. CPINIT is the program that supervises all like-customized devices on the LAN (e.g. other NEBs installed in other open-architecture printers). CPINIT accomplishes this task by communicating over the network with other NEBs that reside within open-architecture peripheral devices. CPINIT is used to configure each NEB with the appropriate basic configuration information such as configuring the NEB as CPSERVER or CRPRINTER. The basic configuration information comprises NEB environment settings (including which print server applications are active), as well as device environment options (e.g. a list of fonts and emulations to download printer initialization time), and device default settings (such as the internal device time/date/time zone, buffer size, disk and logging information, and printer name). The CPINIT program also displays status information about the NEB (such as the firmware level loaded in the NEB and reports latent POST errors). The CPINIT program will broadcast over the network to see which other customized devices are available on the LAN. The NEBs attached to such other customized devices will respond with their identification numbers, their device types, and their configuration states. CPINIT will construct a list of these NEBs and devices that will be presented to the network administrator to allow their configuration or reconfiguration. A DOWNLOADER program may also be loaded into the network administrator's PC 14 to download executable files to the NEB across the network (to be discussed in greater detail in section 4n below). Another customized program which may run on the network administrator's PC 14 is CPFLASH which may be used to remotely flash new firmware into EPROM 222, as will be discussed in greater detail in section 4q below. 4. OPERATION At first, an overview discussion of the NEB structure and functions will be provided with respect to the flowchart of FIGS. 5A, 5B and 5C. Thereafter, more detailed descriptions of various aspects of the NEB hardware and software will be provided with respect to sections 4a to 4q. The present invention takes advantage of the bi-directional nature of the communication between the printer and the NEB, and the NEB's ability to process information on a multi-tasking basis. That is, the bi-directional SCSI bus can transmit large quantities of data both to and from the printer, enabling the NEB to receive large quantities of specific status data from the printer or even data input from the peripheral (such as image data input from a scanner). The NEB microprocessor processes information on a multi-tasking basis (sequential but shared) effectively parallel processing information received from the network and information received from the printer. This multi-tasking processing insures that the NEB is responsive to both the network and the printer on a near real-time basis. FIGS. 5A, 5B, and 5C comprise a top-level flowchart depicting a notional sequence of events which may occur when the NEB and its associated software is installed in a printer coupled to a local area network. Overall, the printer renders print information and is coupled to the NEB through a bi-directional SCSI interface. The printer may also have a parallel port and/or a serial port for receiving print information from other sources. The NEB is connected to the printer via the bi-directional SCSI interface, the board receiving printer information from the local area network. The board sends print jobs and printer status inquiries to the printer over the SCSI interface, receives printer status from the printer over the SCSI interface, and reports printer status over the network. Where the NEB is coupled to a data generating device such as a scanner, the board is connected to the scanner through the bi-directional SCSI interface and is coupled to the network via the LAN interface. The board receives status request information from the network and will pass this information to the scanner over the bi-directional interface. The board will also receive the data generated by the scanner over the bi-directional interface, and will pass that data onto the network over the LAN interface. Illustrating a sequence of events which may occur when the NEB is installed in a printer, FIG. 5A begins when power is applied to the NEB at Step S1. At Step S2, the NEB executes a power-on-self-test ("POST") from EPROM 220. At Step S3, if the POST is successfully completed, the process moves to Step S5 where the NEB EPROM 222 operational code reads the network and printer configuration code from NVRAM 228. If the POST is not successfully accomplished at Step S3, a failure indication is logged at Step S4 and this information may be transmitted to the network over the LAN interface. An LED failure/diagnostics light on the NEB or printer may also be activated. After the network and configuration code have been read from NVRAM 228, the procedure advances to Step S6 where the NEB EPROM operational code reads selected configuration modules, protocol stacks, housekeeping modules, etc., (e.g., the MONITOR multi-tasking module, CPSOCKET, CPSERVER, etc.) from EPROM 222, and downloads the selected modules to DRAM 220. In Step S6, a configuration is selected (in accordance with the configuration set by CPINIT) which defines an operational mode (e.g. CPSERVER or CRPRINTER) of the interactive network board. As will be discussed in greater detail in section 4d below, a binary configuration code is sent over the LAN and stored in NVRAM 228. After the NEB is booted up, the configuration code is read from NVRAM using ROE-resident power-up process steps. Using the ROE-resident process steps, ROM-resident executable modules are selected in accordance with the configuration code read from NVRAM. The modules are selected in bit-wise correspondence to the binary digits of the configuration code in NVRAM. The selected modules are then stored into DRAM and execution control for the modules is passed to DRAM whereupon the selected modules are executed. In this manner, multiple configurations can be defined and selectively changed. At Step S7, the EtherNet frame type of the information packets transmitted on the LAN is determined (as will be discussed in greater detail in section 4e below). That is, EtherNet supports four different frame types: EtherNet 802.3; EtherNet II; EtherNet 802.2; and EtherNet SNAP. To determine the EtherNet frame type, a pre-scan process ("PRESCAN") determines what frame type is resident on the LAN (from any LAN broadcast data), and configures the appropriate NEB-resident protocol stack for that data. The pre-scan process strips away bytes of data from a received LAN packet until the bytes which indicate frame type are reached. Briefly, Step S7 provides the NEB with the capability of processing LAN packets of different frame types by: receiving from the LAN a frame of data, pre-scanning the frame to determine the frame type, and processing, on the NEB, the identified frame, using an appropriate processing program. The pre-scanning operation includes the sub-steps of stripping a predetermined number of bytes from the head of the frame, processing the stripped frame to identify an identification code indicative of the frame type, and transmitting the identified frame to the processing program. At Step S8, a timer module which was downloaded in Step S6 finds the nearest LAN server and requests the current time. After receiving the current time, the process proceeds to Step S9 where it is determined whether it is midnight, i.e. whether the returned time indicates a new date. Steps S9 through S12 comprise a so-called "autologging" function which is carried out in the NEB by the CPSOCKET program in order to automatically and systematically provide status information from the printer to the LAN (autologging will be discussed in greater detail in section 4k below). In Step S9, if midnight has not been reached the procedure advances to Step S13. However, once midnight is reached, the NEB microprocessor 216 transmits a request to the printer over the SCSI bus for the printer to return current status to the NEB. For example, the printer may return the cumulative number of pages printed to the NEB. In Step S11, the NEB microprocessor 216 calculates printer statistics such as pages per job or pages per day, the NEB having kept track of the number of jobs sent to the printer and the date. At Step S12, the printer statistics are transferred to a non-volatile memory such as the printer's hard disk 114 or NVRAM 111, or the NEB's NVRAM 228. Alternatively, Steps S10, S11, S12 may be performed before Step S9, so that statistics are stored every minute. Summarizing Steps S9 through S12, a method for logging system statistics of a printer connected via a bi-directional interface to an interactive network board for LAN communication includes the steps of counting in the printer the number of pages printed, and counting on the board the number of jobs printed. The printer is interrogated daily over the bi-directional interface for the number of pages printed, and the board then calculates daily statistics using the number of pages, the number of jobs, and other status information. The daily statistics are then stored and may be accessed and remotely displayed using CPCONSOL from the network administrator's PC 14. An additional feature of the "autologging" function is that different levels of statistics may be logged. For example, at a basic level, only the number of pages for each job may be logged. At more advanced levels, the number of pages per job plus a log of failure conditions may be logged; or the job start and end times may be logged in addition to the failure conditions and the number of pages per job. The logging level is set by CPINIT. In FIG. 5B, at Step S13, the SAPSERVER program (to be discussed in greater detail in section 4g below) advertises the NEB as having both CPSERVER and CPSOCKET identities. Thus, the NEB and attached printer can function in its twin roles of PSERVER and customized entity (CPSOCKET; i.e., similar to other LAN peripherals having a NEB installed therein). SAPSERVER is a NEB-resident TSR program that allows more than one server to advertise network services at the same time on the same node. Thus, CPSOCKET and CPSERVER both advertise their services through SAPSERVER and respond to inquiries from other network applications. Since each EtherNet board can have only one SAP socket number, SAPSERVER will function to advertise both NEB identities without confusion to the LAN. In summary, Step S13 is a method of identifying a single interactive network board as two network servers (e.g. CPSERVER and CPSOCKET) comprising the steps of transmitting to the network at a predetermined time interval a signal indicating that the board is a first type of network entity, the signal including an identification signal unique to the board; then, transmitting a second signal to the network at the predetermined time interval to indicate that the board is a second type of network entity, the second signal also including the same unique identification signal. Once a signal is received from the network requesting that the board perform functions of one of the types of network entities, direct communication is established between the board (acting as the requested type of network entity) and the network entity which generated the request. When the direct communication is established, the NEB will utilize a new unique identification signal. At Step S14, both the LAN and the SCSI interfaces are checked for data that is being directed to CPSOCKET (to be discussed in greater detail in section 4j below). The SCSI interface will typically have printer status data which is to be passed to the LAN in response to a previously-received request for status. CPSOCKET is the NEB-resident TSR program that responds to such requests for connection, requests for data download, or requests for services from remote utilities. CPSOCKET gathers information from the NEB or the printer, as needed, monitors requests to write to the log file, monitors application requests for device status, and maintains job statistics, as discussed above. Briefly, the CPSOCKET program is a method of interfacing an interactive network board between the network and a peripheral device, comprising the steps of transferring a program from board ROM to board RAM for execution from the RAM; and monitoring, with the program, a board network interface to detect a network communication directed to the peripheral device. The program then commands the peripheral device to perform a function in response to the network communication, and monitors a board bi-directional peripheral interface to detect and store status information of the peripheral device. Finally, the program outputs the peripheral device status information onto the network through the network interface in response to another network communication. In FIG. 5B, Steps S15 and S17 indicate "run-time" layer functions, and Step S20 represents a "soft-time" application layer. First, Step S15 determines whether data is being received over the LAN. When LAN data is received, the process proceeds to Step S16 and the software protocol type is determined (to be discussed in greater detail in section 4f below). For example, the Ethernet data received over the LAN may be one of the following software protocols: e.g. NetWare.RTM. over SPX/IPX; UNIX over TCP/IP; or Mac Systems 7 over AppleTalk. Basically, the software protocol type may be determined according to the frame packet type sensed in Step S7 above. If CPSOCKET determines that LAN data is not being received in Step S15, Step S17 determines whether SCSI data is being received, and if SCSI data is being received, it is input from the printer in Step S18, and then stored in DRAM 220 in Step S19. After the storing of printer data in Step S19, or if SCSI data is not being received in Step S17, the process proceeds to Step S20 where "soft-time" tasks are performed on a multi-tasking basis as controlled by a multi-tasking software program called "MONITOR" (to be discussed in greater detail in section 4l below). Step S20 is therefore a "background" process which runs concurrently throughout the flowchart depicted in FIGS. 5A, 5B and 5C. That is, whenever "soft-time" tasks are being performed, the microprocessor 216 will ensure time-shared, parallel, non-preemptive processing of the "soft-time" tasks. More particularly, MONITOR is a software module downloaded from EPROM 222 to DRAM 220 in Step S6. MONITOR is a non-preemptive multi-tasking monitor which distributes the processor usage among the several application tasks which are currently active. The non-preemptive nature of the monitor requires that each application task periodically relinquish control so that other tasks gain the opportunity to execute. The relinquish control mechanism is implemented using a software interrupt to pass control to the MONITOR. At an interrupt, MONITOR saves the state of the current task, restores the state of another active task, and resumes (or commences) execution of the new task. The task which originally relinquished control eventually regains control at the interrupt point, i.e. with its context restored to the same condition as when it relinquished control. In summary, Step S20 comprises the step of monitoring a plurality of application tasks in a multi-tasking interactive network board to distribute processor resources. A memory stores a first application task which may queue a file server to get a network interface to obtain a queue of print files to be printed, and which channels the print files to a printer coupled to the board through an interface. The memory also stores a second application task which may receive remote status inquiries over a LAN interface, interrogate the printer over a bi-directional interface to obtain printer status and a response to the received status inquiry, and provide the status information over the LAN interface to the status requester. The first and second application tasks each include a relinquish command which causes the currently executing application task to periodically relinquish control to the MONITOR. The MONITOR saves the state of the relinquishing task, restores the state of the non-relinquishing task, and resumes execution of the non-relinquishing task. In FIG. 5C, presuming that data has been received over the LAN at Step S15, Step S21 determines whether the received data is for a print job or not. If it is for a print job, microprocessor 216 acts as the LAN file server for an active print file and transfers print job blocks to DRAM 220 at Step S22. At Step S23, microprocessor 216 assembles blocks of image data and control information, and sends the blocks to the printer through the SCSI interface. In this step, the microprocessor 216 effectively adds "beginning of job" and "end of job" indications to the data stream received over the LAN. It does this by opening the XP (data) channel at the beginning of a print job, and by closing the XP channel at the end of a print job. At Step S24, the process waits until the print job is complete. Once the print job is complete, Step S25 will unambiguously set the printer to a default environment. It is also possible to set the default configuration before (or during) the print job. That is, the NEB itself will ensure that the attached printer is set to a default environment which specifies, for example, default fonts, papers trays, collation, stapling, etc., to insure that the next print job will be started with the printer in a known configuration (to be discussed in greater detail in section 4m below). Step S25 may be thought of as guaranteeing a safe environment for the printer by ensuring that the printer settings (e.g. portrait mode, duplex, etc.) are returned to between logical printing jobs. For example, while Novell NetWare.RTM. includes the ability to prefix every job with printer escape sequences to reset the printer environment, such escape sequences reside in a database on the network file server, and the print job in question might not originate from that file server. In order to ensure a guaranteed safe environment, the NEB will store the requisite configuration parameters, and will be responsible for resetting the printer environment between print jobs. In summary, a method for providing a default configuration to a LAN printer having an interactive network board coupled thereto includes the step of receiving a default configuration over a LAN interface at the interactive network board. The default configuration may be stored in NVRAM 228 in the NEB or stored in an NVRAM or disk in the printer over the bi-directional interface between the board and the printer. Then, the default configuration is downloaded from the NVRAM in the printer to the DRAM 220 on the board over the bi-directional interface. When the board receives print information over the LAN interface and provides the print information to the printer over the bi-directional interface, the board detects an end of print job. In response to this detection, the default configuration is sent to the printer whereby the printer is set in its default configuration. Additionally, a plurality of default configurations may be stored, and an appropriate default configuration may be selected remotely from another LAN entity. For example, a method of setting one of a plurality of default configurations may include a step of detecting, at the board, the origination of a print job and identifying the source of the job. Subsequently, an appropriate default configuration is selected from among the stored configurations, and the selected default configuration is then sent to the printer at the beginning or end of the print job. In FIG. 5C, if it is determined that a print job is not required at Step S21, Step S26 determines whether a status request has been made over the LAN requesting the status of the attached printer. If it is determined that a status request has been received, Step S27 determines the type of status request. For example, printer status such as error codes, the number of pages printed, the toner status, etc., may be requested. At Step S28, the microprocessor 216 retrieves the requested status data from DRAM 220, assembles the status data, and sends it to the LAN through the LAN interface (to be discussed in greater detail in section 4i below). Thus, in Step S28, more than simple "on/off" information may be transmitted to the LAN so as to inform the LAN of the detailed status of the printer. In a broad application, Step S28 encompasses the export of printer front panel status over the LAN, and the import of front panel control commands from the LAN. That is, the network administrator at the PC 14 may request and receive a display indicating all of the printer information included on the printer front panel display 116. The network administrator may then activate different printer front panel functions on his/her PC, and such functions will be transmitted to the printer where the selected control will be effected. In summary, at Step S28, a method for remotely controlling a manually-operable function of a networked printer through an interactive network board having a LAN interface for LAN communication, comprises the step of issuing, at a remote location, a command to the board that will cause the board to transfer printer status information through the board to the remote location through the LAN interface. At the remote location, a printer status may be displayed, and a second command may be issued at the remote location to the board through the LAN interface to cause the board to perform a manually-operable function. If the received LAN data is neither a print job nor a status request, it is determined at Step S29 that the received data may be a download operation, i.e., a transfer of data into the NEB for updating the ROM or RAM applications, e.g. download may be utilized for transient diagnostics to be run on the NEB. First, at Step S30, the data is downloaded from the LAN to the DRAM 220 (to be discussed in greater detail in section 4n below). That is, the download is a process by which data may be loaded into a network node and then acted upon or executed. For example, anything from patch code, to manufacturing test routines, to firmware updates for the EPROM may be downloaded. Also, application modules may be stored in the LAN file server and then downloaded to the NEB every morning. In summary, the downloading of data from LAN to DRAM comprises a method for altering an operational mode of an interactive network board having a LAN interface, including the step of activating a LAN communication program for execution from DRAM, the communication program channelling print information on the LAN to a peripheral printer. Executable instructions which correspond to the altered operational mode are then downloaded into DRAM via the LAN interface. The board is then commanded via the LAN interface to begin execution of the altered operational mode. At Step S31, it is determined whether the downloaded information is destined for EPROM 222 or DRAM 220. If the information is destined for EPROM, a ROM image is assembled at Step S32 (to be discussed in greater detail in section 4 o below). For example, downloading of EPROM firmware from a remote location provides unique flexibility. In particular, downloading of on-board test routines, and changing EPROM configuration firmware can be performed from a remote location after the board is installed in the printer. Step S32 is the process which constructs the binary image file which is to be programmed into the EPROM 222. The data destined for the EPROM is first downloaded to DRAM 220 where a utility reads a configuration file containing the names of the modules to be placed in the ROM image. Then, a complete binary image file is constructed containing all of the specified modules. A header precedes each module in the image, the header identifying the module, describing its attributes, and pointing to the succeeding header to aid in locating the modules during loading. The last module loaded in the EPROM is the EPROM-resident code. It is placed at the end of the ROM image so that the power-up initialization code resides at the address expected by the microprocessor 216. In summary, Step S32 comprises a process for formatting a binary image file which contains executable code modules for storage in the EPROM. First, a configuration file is read which specifies the code modules which form the binary image. Next, a header is formed for each module specified in the configuration file, the header including an identification of the module, a definition of the module's attributes, and a pointer to a header for a succeeding module. The binary image file is then constructed containing the specified modules and their associated headers. Finally, a module of ROM-resident code is appended to the binary image, the ROM-resident code receiving control at power-up, providing POST, loading at least some of the modules from the binary image file into DRAM 220, and providing basic board I/O services. Before writing new data into EPROM 222, it is first necessary to unequivocally ensure that a write operation is, in fact, intended. Obviously, any accidental writings into EPROM 222 could render the NEB unusable. Therefore, before information may be "flashed" to EPROM 222, a specified sequence of events will occur in Step S33 in order to access the EPROM (to be discussed in greater detail in section 4p below). In the present embodiment, unless two data bits are changed in two separate I/O locations, the +12 Volts necessary to write to the EPROM will not be provided. Briefly, a method of ensuring that the EPROM is not accidentally written into comprises a method of performing a flash operation on an EPROM resident on an interactive network board having a processing unit and a memory, including the step of sending an I/O write signal to the processing unit. Then, the processing unit generates a first address in the memory to cause a first bit to be in a predetermined state in response to the I/O signal. A power unit is then caused to provide +12 Volts to a transistor in response to the first bit being placed in the predetermined state. Then, an I/O receive signal is sent to the processing unit which generates a second address in the memory to cause a second bit to be in a preselected state in response to the I/O receive signal. Then, the transistor is turned on in response to the second bit being placed in the preselected state causing the +12 Volts to flow to a power terminal of the EPROM, allowing a write operation to take place. Before the new ROM image is actually stored in EPROM 222, at Step S34 the new ROM image must be checksummed and verified with a checksum value sent after the ROM image is received. Prior to erasing EPROM 222, data and modules to be preserved, such as the MAC address, must be loaded into DRAM 220 within the new ROM image. After determining that the ROM image is verified and after preserving all required data into the new ROM image stored in DRAM 220, it is necessary to clear and erase EPROM 222 to ensure no corruption of data upon loading of the new ROM image. Accordingly, at Step S35, EPROM 222 may be erased a plurality of times before the new ROM image is stored therein. After erasing EPROM 222 at Step S35, the new ROM image is "flashed" into EPROM 222 in Step S36 (to be discussed in greater detail in section 4q below). In summary, Step S36 relates to a method for remotely altering programmable firmware on an interactive network board having a LAN interface including the step of activating a LAN communication program for execution from DRAM on the board, the communication program channelling print information on the LAN to a peripheral printer. A ROM firmware image is then downloaded to the DRAM on the board via the LAN interface. It is next confirmed that the ROM image has been downloaded to the target board, and the integrity of the ROM image is confirmed. The board is then commanded to electronically erase the EPROM, and then the EPROM is flashed with the new ROM image. Additionally, a "flash complete" signal may be sent to the LAN after the flash operation, if desired. After the information is flashed to the EPROM 222, the NEB is then re-booted from the new ROM firmware image in EPROM 222 at Step S37, and the process returns to Step S1. In FIG. 5C, if Step S31 determines that RAM information is being downloaded, such information is first assembled in DRAM 220 via Step S38. Subsequently, Step S39 executes the RAM program, and the process returns to Step S13 wherein SAPSERVER advertises PSERVER and CPSOCKET entities. This discussion concludes the overview of the NEB structures and functions when the NEB is installed in LAN-networked printer. A more detailed description of the operation of various aspects of the NEB hardware and software will now be provided. 4a . Power-on Sequence Immediately following power-on, NEB 2 executes a power-on self test (POST), following which the NEB loads operational software from EPROM 222 into DRAM 220 for execution. More specifically, immediately following power-on, microprocessor 216 accesses POST program modules located in EPROM 222. Microprocessor 216 executes POST directly from EPROM 222 to test the functionality of the microprocessor, integrity of the programs stored in EPROM 222 (for example, via checksum verification), operability of DRAM 220 (for example, through read/write cycles), operability of SCSI controller 224, data integrity of NVRAM 228, and operation of control register 230. POST may also include a comparison of the MAC address stored in PROM 232 with a MAC address downloaded into EPROM 222. POST further includes operational checks of network-related hardware. More specifically, POST may include operability checks for SRAM 214 (for example, through read/write cycles), as well as a check of network activity to verify operation of network controller 206. Operation of other hardware in NEB 2 may be determined directly through additional POST testing. In some cases, where it is not possible for microprocessor 216 to test operation of hardware directly, as in the case of connectors 202, 203 and 204, proper operation of that hardware may be implied through result codes received from direct testing. Upon termination of POST, microprocessor 216 puts a checksum code onto serial port 218 and then enters a window of quiescent operation (for example, a one second window) during which microprocessor 216 can receive commands (e.g. for testing--see paragraph 5 below) via serial port 218. The POST checksum code may be obtained by a device coupled to serial port 218 to determine the outcome of POST. For example, a no error condition may be indicated by a POST checksum code of "0000 h", while a POST checksum code indicating an error may be indicated by a non-zero hexadecimal value which indicates the area of failure. In the case of failure, microprocessor 216 may also illuminate LED 240 on NEB 2 to signal to a user that an error has been detected. Preferably, LED 240 is illuminated on power-up and is only turned off if POST is successful. Following successful completion of POST and in the event that no commands are received via serial port 218 during the one second quiescent window of activity, microprocessor 216 begins to load software modules stored in EPROM 222 into DRAM 220. Microprocessor 216 does not execute those software modules directly from EPROM 222, but rather loads those modules into DRAM 220 for execution from DRAM 220. By virtue of this arrangement, it is possible to select the specific modules that are retrieved from EPROM 222 for execution out of DRAM 220 so as to permit flexible configuration of NEB 2 (see section 4d below). For example, in accordance with a configuration command stored in NVRAM 228, microprocessor 216 may retrieve selective modules from EPROM 222 for loading into DRAM 220 and for execution from the DRAM. FIG. 6 shows the sequence by which different modules are retrieved from EPROM 222 and loaded into DRAM 220. In Step S6001, microprocessor 216 loads the SCSI driver from EPROM 222 into DRAM 220. The SCSI driver provides for operational sequence and control over SCSI controller 224 and permits interface with printer 4 so as to send printer 4 print data and so as to send and receive control information to and from printer 4. In Step S6002, microprocessor 216 loads the link support layer, or "LSL", from EPROM 222 into DRAM 220, and in Step S6003 microprocessor 216 loads network driver software from EPROM 222 into DRAM 220, and thereupon microprocessor 216 begins to execute the link support layer and the network driver from DRAM 220. The link support layer and the network driver provide common access to LAN communications on LAN bus 6. More particularly, as shown in FIG. 7, all networked devices, including a device such as NEB 2, interface with LAN bus 6 via an electrical interface 301 such as the network controller 206 used on NEB 2. The electrical interface 301 is driven by network driver 302 which in turn receives LAN frame data from link support layer software 304. Both the link support layer 304 and the network driver 302 are common to different kinds of network software. For example, as further shown in FIG. 7, network application programs, such as those provided in NetWare.RTM. software by Novell (as illustrated at Arrow A) interface with the link support layer and the network driver via an internetwork packet exchange program, or "IPX", 305 and a sequenced packet exchange program, or "SPX", 306. On the other hand, network application programs from UNIX provided by AT&T (as illustrated at Arrow B) interface to the LSL through "IP" module 315 and "TCP" module 316. In NEB 2, only one type of network application programs is normally executed at any one time (although multiprotocol operations are possible as discussed in section 4f below). Explanation here will be made for NetWare.RTM. network application programs although it is also possible for UNIX network application programs to be executed as well. In Step S6004, microprocessor 216 loads a PRESCAN program from EPROM 222 and stores it into DRAM 220, and thereupon begins executing the PRESCAN program from DRAM 220. PRESCAN software interfaces with the link support layer to determine the frame packet type being transmitted on LAN bus 6. More particularly, as described above, there are four different possible frame packet types on an Ethernet-type network LAN bus: Ethernet 802.3, Ethernet II, Ethernet 802.2, and Ethernet SNAP. As described more fully below in section 4e, the PRESCAN software module monitors network communications on LAN bus 6 to determine the frame packet type. The frame packet type, once determined by PRESCAN, is stored in a predetermined common location in DRAM 220 for use by other network communication modules in the NEB. After determining the frame packet type, PRESCAN signals microprocessor 216 that its tasks are completed and allows microprocessor 216 to overwrite the memory occupied by the PRESCAN program with another program module. In Step S6005 microprocessor 216 retrieves the IPX and SPX program modules from EPROM 222 and stores them in DRAM 220, and thereupon begins executing the IPX and SPX modules from DRAM 220. Both IPX and SPX use the frame packet type determined by the PRESCAN module. In Step S6006 microprocessor 216 retrieves the CNETX program module from EPROM 222 and loads that module into DRAM 220 and thereupon begins execution from DRAM 220. CNETX provides localized DOS-like functionality to the NEB. In Step S6007, microprocessor 216 loads the SAPSERVER program module from EPROM 222 into DRAM 220 and begins executing the SAPSERVER module from DRAM 220. As described more fully below in section 4g, SAPSERVER is a program module which allows two network server entities, such as CPSOCKET and CPSERVER, to advertise simultaneously from the single network node assigned to the NEB board, even though conventional network application programs such as those provided by NetWare.RTM. only permit advertising of a single network server entity from each network node. In Step S6008 microprocessor 216 retrieves the non-preemptive multi-tasking MONITOR (see section 4l below) from EPROM 222 and stores it into DRAM 220 and begins executing the multi-tasking monitor from DRAM 220. In Step S6009 microprocessor 216 retrieves the CPSOCKET server software module from EPROM 222 and loads it into DRAM 220 and begins executing the CPSOCKET server from DRAM 220. As will be described more fully below in section 4j, CPSOCKET initiates a request to SAPSERVER to advertise on behalf of CPSOCKET, and SAPSERVER begins making SAP advertisements on LAN bus 6. In Step S6010 microprocessor 216 retrieves print application servers such as CPSERVER or CRPRINTER from EPROM 222 and loads the print application servers into DRAM 222. In the case of CPSERVER, microprocessor 216 begins executing the loaded print application servers from DRAM 220 which in turn requests SAPSERVER to make SAP advertisements on behalf of the print server. As described more fully below in section 4g, SAPSERVER interleaves advertisements for the CPSOCKET server and for the print server thereby acting as a surrogate SAP entity for both the CPSOCKET server and the print server. 4b. Interface A Peripheral With A Local Area Network According to the broad aspects of the present invention, a peripheral such as a printer is coupled to a LAN using an interactive network board having software programs embedded therein. Preferably, the connection between the printer and the NEB is an SCSI interface so that large amounts of print data and status data are carried bi-directionally between the NEB and the printer. EPROM 222 stores a plurality of software modules for operationally configuring the NEB in the PSERVER or RPRINTER or LPR functional configurations. The EPROM 222 also stores a number of status control software modules for exporting status information from the printer over the LAN, and for importing control information from the LAN to the printer. The EPROM-resident firmware is downloaded to the DRAM 220 upon power-up (as discussed in section 4a above), whereby the MONITOR multi-tasking program executes soft-time tasks until run-time interrupts are received from either the LAN or SCSI interfaces. NVRAM 228 stores a configuration word which specifies which modules stored in EPROM 222 should be downloaded into DRAM 220 in order to configure the NEB with either a PSERVER or RPRINTER functionality. The microprocessor 216 executes the programs from DRAM 220, allowing print jobs to be received from the LAN and sent to the printer for printing, and allowing printer status to be returned over the LAN in response to a status request. The particular details of the structure and functions for interfacing the peripheral to the local area network are set forth above with reference to FIGS. 4, 5A, 5B and 5C, and in the following sections. 4c. The Bi-Directional Interface Between The Local Area Network and the Printer The provision of a bi-directional SCSI interface between the NEB 2 and the printer permits a large amount of status information to be extracted from the printer, while still providing the print data to the printer. Further, by utilizing the bi-directional SCSI interface, the printer can respond to control commands issued from a remote location over the LAN. For example, the network administrator may issue a control command from his/her PC 14 that requests a particular print job be printed a plurality of times, with high image density, and then stapled. Such control commands are sent to the NEB 2 over the LAN 6, and the NEB 2 transmits these control commands to the printer through the SCSI bus 102. At the same time, the actual print data is transferred from file server 30 to the NEB 2, where the print data is packaged in blocks and transferred to the printer over the SCSI bus 102. Preferably, the NEB 2 indicates the "start of print job" by opening the XP data channel to the printer. Likewise, the NEB 2 indicates "end of print job" by closing the XP data channel to the printer. Therefore, the NEB 2 can provide such indications to the printer. The use of the bi-directional SCSI interface on the NEB 2 also permits other types of peripherals to be coupled to the LAN. For example, since the SCSI interface is capable of transmitting large quantities of data to the LAN from the peripheral, it is possible to couple the NEB to an image data generating device such as a scanner (e.g., where printer 4 is an Optical Character Recognition ("OCR") device) or a facsimile machine. Thus, data produced by the image generating device may be transferred to the NEB over the SCSI interface, and then put on the LAN for storage or retrieval by any of the LAN entities. As with a printer, large quantities of detailed control/status information can also be provided to/from the image data generating device. The detailed structural and functional features of the bi-directional SCSI interface on the NEB are set forth above with reference to FIGS. 4, 5A, 5B and 5C, and in the following sections. 4d. ROM Firmware Configuration As described earlier with respect to FIG. 5A, Step S6 downloads selected software programs from EPROM 222 to the DRAM 220 for execution (see also FIG. 6 and section 4a ). The EPROM 222 is delivered with firmware modules which permit the NEB 2 to be configured with either RPRINTER or PSERVER functionality. Therefore, the functionality of the NEB 2 will be determined by which of the stored programs are downloaded from EPROM 222 to DRAM 220 in accordance with the configuration code stored in NVRAM 228. The NEB 2 firmware is configured initially, and can be reconfigured subsequently by running CPINIT on the network administrator's PC 14 (see section 4h below). However, even in an unconfigured state, NEB 2 itself will always activate those software modules needed to perform basic communication with the LAN. Using CPINIT, the network manager can determine, remotely, the current configuration of the NEB, or he/she can change the configuration as desired. Since the configuration information is stored in EPROM on the NEB board, the configuration information is retained across power cycles. The process by which the software programs for a particular configuration are downloaded from the EPROM 222 to the DRAM 220 will be described below with respect to FIG. 8. After the board has been powered up at Step S1, the process proceeds to Step S8001 where microprocessor 216 accesses EPROM-resident code in the EPROM 222 to read a configuration code (typically a word) from NVRAM 228. The configuration code will specify modules which can provide the NEB with either a PSERVER or RPRINTER functionality. Although the present embodiment includes only RPRINTER or PSERVER functional configurations, other configurations may be utilized where, for instance, the NEB 2 is installed in a different LAN entity, such as a scanner or a facsimile machine. After reading the configuration code from NVRAM 228, the microprocessor, at Step S8002, forms a configuration mask whose bit pattern corresponds to the read configuration code. At Step S8003, a loader module resident in EPROM 222 compares the configuration mask to the plurality of firmware modules stored in the EPROM 222. In detail, in Step S8004, a process begins whereby the EPROM-resident software modules are selected in bit-wise correspondence to the binary digits of the configuration code read from NVRAM 228. If it is determined in Step S8004 that the currently-examined bit of the bit pattern matches a stored module, then that module is selected (at Step S8005) for downloading to DRAM 220, and the process skips to the next bit at Step S8006. Likewise, if Step S8004 determines that a bit of the bit pattern does not match the stored module, the process skips to the next bit at Step S8006. At Step S8007, it is determined whether the bit tested in Step S8004 is the last bit of the configuration mask bit pattern. If the tested bit is not the last bit, the process loops back to Step S8004, where the next bit of the bit pattern is tested with respect to the next stored module. When the last bit of the configuration mask bit pattern has been tested, the selected software modules are downloaded from EPROM 222 to DRAM 220 at Step S8008. In the present embodiment, the software modules are loaded in the following sequence: SCSI Driver; Link Support Layer; Network Driver; Prescan; IPX/SPX; CNETX; SAPSERVER; MONITOR; CPSOCKET; and Print Applications (e.g CPSERVER, CRPRINTER) (see FIG. 6). After all of the software modules which correspond to the configuration codes stored in NVRAM 228 have been downloaded to DRAM 220, the loader function will pass program execution control to the MONITOR multi-tasking program at Step S8009. As discussed earlier, the configuration code stored in NVRAM 228 may be remotely altered using CPINIT. This provides greater flexibility for making minor modifications to CPSERVER or CRPRINTER, or where entirely new configurations are desired to be set. Therefore, at Step S8010, a new configuration is received over LAN 6, and is loaded into NVRAM 228 at Step S8011. Preferably, the old configuration code will be erased or overwritten with the new configuration code. Then, the NEB re-boots itself and returns to Step S1. 4e. Determining Frame Packet Type Using PRESCAN On any local area network, data is transmitted between network devices in packets or frames. But even in the context of a common network architecture, such as Ethernet, more than one format for the frame may be supported. Thus, even though it is known that Ethernet architecture is being used, it is not possible to determine the arrangement of data within each physical frame or packet of information on the Ethernet bus. In particular, as described above, Ethernet supports four arrangements of data, or formats, as follows: Ethernet 802.3, Ethernet II, Ethernet 802.2, and Ethernet SNAP. In conventional network devices, which provide for a manually selectable operator interface, it is possible to advise the network device of the particular frame type being used on the Ethernet network. In the context of NEB 2, for which operator access is provided only via the network interface (or via the serial port 218 in a test configuration), it is not possible to set the frame packet type without first allowing operator access to the local area network which, of course, requires knowledge of the frame packet type. The PRESCAN software module allows NEB 2 to automatically determine the frame packet type currently being used for LAN communication on the LAN bus by monitoring broadcast communications on the LAN bus until the proper frame packet type is recognized. PRESCAN makes this determination based on recognizable components that are common to all four frame packet types used on Ethernet. In more detail, FIG. 9 shows the physical construction of different frame packets used on Ethernet. As shown in FIG. 9, a physical frame 411 being transmitted on the LAN bus includes a 6-byte section 412 for storing the destination MAC address, and a 6-byte section 413 for storing the source MAC address. These 12 bytes comprise the first 12 bytes of LAN data packets regardless of the frame type being used for LAN communication. A data section 414 follows these 12 bytes. The data section is comprised of a variable number of bytes which are not used for the same purposes by the different frame packet types and which do not have the same number of bytes for the different frame packet types. Following the indeterminate area 414, the LAN communication packet includes an IPX header 415 the first two bytes of which always has the value "FFFF" (hexadecimal). The remainder of the packet 416 follows the IPX header and comprises the data and other commands which characterize each different type of LAN communication packet. PRESCAN operates by monitoring the LAN communication in accordance with each of the different packet types until the common area (such as IPX header 415) is recognized in one of those packet types. PRESCAN then stores that packet type for use by other network communication programs. FIG. 10 is a detailed flowchart for showing operation of the PRESCAN module. In Step S1001, microprocessor 216 retrieves the PRESCAN module from EPROM 222 and loads it into DRAM 220 and thereupon begins execution of the PRESCAN module. The PRESCAN module is executed before the SPX and IPX modules, even if microprocessor 216 retrieves those latter modules from EPROM 222 and loads them into DRAM 220 before the operational sequence shown in FIG. 10 is complete. More particularly, proper operation of the SPX and IPX program modules depends upon the identification of the frame packet type by PRESCAN and therefore execution of SPX and IPX is deferred until after PRESCAN determines the proper frame packet type. In Step S1002, PRESCAN simultaneously binds through LSL to all four frame packet types, namely, Ethernet 802.3, Ethernet II, Ethernet 802.2, and Ethernet SNAP. That is, PRESCAN configures LSL such that for each packet of LAN communication, LSL provides a data group corresponding to each of the four frame packet types. Thereafter, PRESCAN goes inactive pending reactivation by an interrupt from the network driver. In Step S1003, the network driver monitors communications on the LAN bus for broadcast traffic. Broadcast traffic means that the destination MAC address 412 is unspecified or is given a global specification of "FFFFFFFFFFFF" (hexadecimal). The network driver continues to monitor communications on the LAN bus for broadcast traffic (Step S1004) until broadcast traffic is received, whereupon flow advances to Step S1005. In Step S1005, the MAC address fields 412 and 413 are stripped off the received data packet and the remainder of the data packet is provided to LSL. In Step S1006, LSL interprets the frame packet in accordance with each of the frame packet types and provides a data group in correspondence to each of the frame packet types. In Step S1007, the network driver reactivates PRESCAN which determines which data group provided by LSL has the proper first two bytes, of an IPX header, namely "FFFF" (hexadecimal). That is, because of the variable data area 414 (variable data area 414 corresponding to each of the different packet types (FIG. 9)), LSL will properly identify the IPX header 415 in accordance with only one of the frame packet types. In Step S1007, PRESCAN searches for the IPX header and, in accordance with which of the four data groups is provided by LSL, it is able to determine a frame packet type that is currently being used on the LAN bus. In Step S1008 PRESCAN stores the corresponding frame packet type in a common area in DRAM 220 so that the frame packet type can be used by other network application programs such as SPX and IPX. Thereafter, in Step S1009, PRESCAN frees its storage area in DRAM 220 so that microprocessor 216 may overwrite that data area with other software modules, if desired. 4f. Multiprotocol Operation In a multiprotocol operation, two different operating systems carry on LAN communications over a single local area network bus, but using respectively different operating protocols. For example, a Novell-compatible operating system communicates over a LAN bus using SPX/IPX operating protocol, while a UNIX-compatible operating system communicates over the LAN bus using a TCP/IP operating protocol. Other operating systems, such as the AppleTalk.RTM. operating system provided by Apple Corporation, use respectively different operating protocols for LAN communication over a single network bus in a multiprotocol network environment. Ordinarily, NEB 2 is configured to communicate to a single network operating system, but it may also be configured to operate in a multiprotocol network environment, for example, a combined Novell/UNIX multiprotocol environment. In this configuration, NEB 2 includes a Novell-compatible peripheral server, such as the aforementioned CPSERVER, which checks job queues in a file server on a Novell operating system, as well as a UNIX-compatible peripheral server, such as the aforementioned CLPR (Custom Line Printer Remote), which, in coordination with checks made by CPSERVER, also checks for job queues in a file server for a UNIX operating system. Both servers, here CPSERVER and CLPR, service common peripheral resources, here a single peripheral such as a printer, and to avoid contention for control of the common resources, both servers are able to seize control of the peripheral to the exclusion of other servers, to signal other servers that control has been seized, and to relinquish control of the peripheral when the job queue has been emptied. It is also possible for each server to check with other servers to determine if other servers have a pending request for use of the peripheral. In the case where there is a pending request, the server can relinquish control of the peripheral at the end of a current job even though there are jobs remaining in the job queue, so as to allow alternating use of the peripheral by each server. FIG. 11 illustrates NEB 2 configured for multiprotocol network operations. FIG. 11 illustrates a combined Novell/UNIX multiprotocol environment, but it is to be understood that other operating protocols may be substituted for or used in combination with those shown in FIG. 11. In FIG. 11, NEB 2 is interfaced to LAN bus 6 via electrical interface 321, network driver 322, and link support layer ("LSL") 324, much as illustrated a | ||||||