Ref: 03190001 Title: Using HP Plotters with 3Com 3+ Networks Date: 12/6/89 Copyright 3Com Corporation, 1991. All rights reserved. As 3+ systems are increasingly used in the fields of presentation graphics and CAD, shared plotter support becomes even more important. 3+ does support shared plotter devices. This note describes the proper integration of a Hewlett-Packard 7550A plotter with a 3Com 3+ network. Other Hewlett-Packard plotter devices work in a similar fashion, so these notes should apply. However, each device differs from the others in sometimes subtle ways, so proper pre-sale testing is always recommended. In particular, different models may require the serial interface to be configured by means of switch settings; the 7550A settings can all be configured from the front panel. Proper interfacing requires the right serial cable, configuration of the plotter's serial interface and configuration of the server's serial interface. Finally, application software configuration may be required. Test Environment Our test environment for this application note was an Ethernet network with a 3Server3 running 3Com's 3+ operating system, version 1.1. The workstation was a Compaq 386. Application Software tested included Software Publishing's Harvard Presentation Graphics, and AutoDesk's AutoCAD. Physical Connection The plotter is connected to the server by means of a serial cable available from Hewlett-Packard as part number 17255F. The cable is female at both ends, and is connected between a shared serial port on the server and the "computer/modem" port on the 7550A. A similar cable, the 17255D, is male at one end and female at the other for connection to models 7470A, 7475A, 7580B, 7585B and 7586B. This latter cable is frequently available and referred to as an "IBM PC/XT to HP Laserjet" cable. Not all of the above mentioned plotter models have been tested on 3+ networks. If the above cable is not available, the following schematic describes the appropriate connections: 1---------------------------------1 2---------------------------------3 3---------------------------------2 7---------------------------------7 5----------|----------------------20 6----------| |---------------5 20-----------------|---------------6 Pins not shown are not used. Server Configuration Using the 3+ Installation and Configuration menus, select Configure Services, Change Share, Configure Printers, and configure a COM: port on the server as follows: --------------------------------------------------------------- | 3+Share Network Printer Config Ver 1.1.1 Memory Used:xxxx | | | | | | Configure COM1: as network printer? Y | | Description Hewlett-Packard 7550A | | Eject a page between jobs? N | | Translate IBM to Laserjet (Form Type) 0 | | | | Form Type 1 Print Banners? N | | Baud rate N Parity 3 | | Protocol Type 1 Retry Count 10 | | Buffer size 4096 Interrupt level 0 | | | | Change reset sequence? N Reset sequence name HP-GL | | Reset retries 10 | | | ---------------------------------------------------------------- Define a custom reset sequence by answering Y in the Change Reset Sequence? field. Name the sequence HP-GL. Define the sequence as follows: 41,46,3B The HP-GL command is AF;. The purpose of this reset sequence is to ensure the automatic loading of a clean sheet of paper (or transparency) at the beginning of a new job if the previous application did not already perform this function. Proper operation of this feature requires that the plotter must be in automatic feed mode (an * must appear in the plotter's display window below the auto feed key, which toggles this option.) Note that the reset sequence does not actually perform a reset (HP-GL: ESC.R) on the plotter. This is because the execution of this command puts the plotter in a state where it accepts characters from the host and loses them until the reset is complete. Although there is a programmatic mechanism a directly connected host can use to determine when it is safe to send more output, the 3+Print despooler does not support this convention. The result of using the reset sequence will be the loss of the first part of a new plot file. It is important to understand then, that if an application places the plotter in a non-standard state and fails to reset it explicitly, results may be unpredictable for subsequent jobs, particularly if they are generated by different applications. Plotter Configuration The HP 7550A has a front panel allowing the user to control many aspects of the plotter's operation. Please refer to the HP 7550 Operation and Interconnection Manual for further information. Proper network operation requires that the plotter is set up with standard defaults, with the following essential parameters: Interface: Standard Serial Data Flow: Remote, Standalone Bypass: Off Handshake: XON/XOFF, Direct Duplex: Half Parity: 8 bits, Off Baud: 9600 To review or change any of these parameters, refer to the HP manual. Generally, you touch the Enter Key immediately followed by the Next Display key to enter the configuration section. There are several submenus that the unlabled keys lead to. Once on a menu where a parameter can actually be changed, an asterisk will flash in the upper right hand corner of the display, near the Enter key. Use the appropriate blank keys to toggle through the available options, press Enter to accept the current choice. To exit that menu without changing anything, press Next Display. To leave the set-up menus and return to the normal plotter operation menus, press Enter, then Next Display. Application Configuration Applications must be configured to send HP-GL formatted output to a device that can be redirected across the network to the shared port. Generally, this device appears to the application as LPT1:, which is linked to the shared device with the 3P LINK command. For Harvard Presentation Graphics, select the HP 7550A as the plotter device, and LPT1: as the output port. Some applications, like AutoCAD, may assume that the only connection to the plotter is serial. This presents a problem, since you cannot redirect output to COM1: across the network. AutoCAD provides a useful workaround, however. When the plotter is configured, answer YES to the question "Plot to file?". When prompted for a file name, supply PRN: as the name. This name can be supplied as the default name as well. Finally, some applications expect interactive communication with the plotter. HP-GL supports queries such as "is the pen up or down?" or "what color pen is loaded?". Spooled devices cannot support such interactivity; results from such applications may be unpredictable. In any case where "plot to file" is an option, that option must assume there can be no interactivity, so it is safe to assume that the application does not require it, at least when in the "plot-to-file" mode.