Following the directions below will yield a cable that, when connected to the printer port on the rear of a VAXstation 2000, automatically switches the console device (OPA0:) from the graphics adaptor to the printer port, thereby allowing the machine to diagnosed, or even operated, bereft of the graphics subsystem. In this mode, the VS-2000 functions substantially similarly to a generic MicroVAX-II.
The cable requires a standard DE-9F 9-pin female connector on the VS-2000 end, and a DB-25F 25-pin female for the other. These parts are readily available at any good electronics store. It's a good idea to use shielded cable if possible.
The following is the connection map for the signals:
VAXstation 2000 | Console Terminal | Signal DE-9F | DB-25F Signal Signal Glossary ------ ------- | -------- ------ --------------- GND 1 ------------ 1 GND GND = GrouND TxD 2 ------------ 3 RxD RxD = Receive Data RxD 3 ------------ 2 TxD TxD = Transmit Data DTR 4 ------------ 5 CTS DTR = Data Terminal Ready DSR 6 ----------- 20 DTR CTS = Clear To Send GND 7 ------------ 7 GND DSR = Data Set Ready Special 8 -| Special 9 -|
Notice that pins 8 and 9 are shorted together at the VAXstation 2000 end of the cable. This enables the change of console port from the graphics system to the printer port. Without this signal, you have a simple printer cable.
Note: Unlike the "standard" PC/AT 9-pin cable, Pin 7 is a ground rather than RTS (Request to Send). Don't try to use a PC cable in this application; it won't work.
The default speed for the port, established at each power- on cycle, is 9600 bps. Any standard terminal, or emulator, may be used. The comms settings are 8 bits, no parity, and 1 stop bit.
Changes may be required to the operating software, especially the startup files, and will differ depending on what version of VMS you're running. On my machine (running MicroVMS 4.7) I had to disable the VWS startup command procedure and change a "$ sysgen autoconfigure all" statement in sys$system:startup.com to "$ sysgen autoconfigure all/sel=(tt,es)" for the machine to boot correctly. Without doing this, the machine would encounter a fatal bugcheck at the sysgen statement.
I am told that in VMS 5.x and beyond there's a sysgen parameter called "WINDOW_SYSTEM" which can be changed so VWS (or DECwindows) won't start. This may be done during a "conversational boot". I can't verify the assertion because all the 2000s I have access to run 4.7. For all I know, 5.x may be immune to the problem altogether.
According to information I received in July of 1998 (Thanks, Peter!) the cause of the bugcheck was the sysgen command querying the keyboard for the graphics subsystem and not seeing it (or getting contradictory information). This, in turn, confused the VAX enough to make it dump core and shut down.
If all else fails, boot the machine in "conversational" mode (>>> b/1 dua0) and do a SET STARTUP_P1 "MIN" followed by a CONTINUE; the VS-2000 will then boot without any devices other than OPA0: and DUA0: configured. Troubleshooting at that point will be possible.