TU58 <-> PC cable pinout

TU58 <-> PC cable pinout

Post by Tim Shopp » Tue, 20 Apr 1999 04:00:00

> Can someone give me the exact pinouts of the cable between a PC serial
> port and the TU58 drive used on the VAX11/730? (DB25 <-> BERG10) I tried
> to build one using the .txt file found on ftp.dbit.com, put I failed,
> I must have misiterpreted something...

There is some very real debugging you can do past "I failed".  
What didn't work?  What did you expect to happen?  What did you
do on the PC?  What did you do on the TU58?  You obviously need
software on the PC that knows how to speak to the TU58 with RSP -
what are you using?  What port/speed is it set to use?

Hook up a terminal, using only lines 2, 3, and 7, and see if you can
communicate with your PC over that.  If your PC is expecting RTS/CTS
flow control, it ain't gonna work with a TU58.

Next step is to ensure that your TU58 is indeed getting +5V
and +12V on the proper power supply pins.

Then check the TU58 electronics to make sure it is using the
serial rate you want.  Here's the wire-wrap pins used to
select receive and transmit:

WW1 150 baud
WW2 300 baud
WW3 600 baud
WW4 1200 baud
WW5 2400 baud
WW6 4800 baud
WW7 9600 baud
WW8 19200 baud
WW9 38400 baud
WW10 UART Receive clock
WW11 UART Transmit clock

Other wire-wrap jumpers select whether RS-422 (balanced) or RS-423
(unbalanced) are in use:

RS-423: WW17 to WW19, and WW18 to WW20.
RS-422: WW21 to WW19, WW22 to WW20, and WW23 to WW24.

You almost certainly want RS-423 for use with a PC serial port.

And it looks to me if you want a 25-pin cable to hook to a PC,
you just need a BC20N-05 style "null modem" cable.  i.e.

10-pin connector                    25-pin connector

XMT DATA +   3 -------------------------------------- 3 RCV DATA

RCV DATA +   8 -------------------------------------- 2 XMT DATA

RCV DATA -   7 --\
  GND        9 --/

  GND        2 -------------------------------------- 7 GND

If this doesn't work, the only possibilty is that you need to switch
2 and 3 around on the 25-pin connector.


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