argh, VAX DB-9 pinout?

From: Eric Smith <eric_at_brouhaha.com>
Date: Wed Dec 15 03:01:24 1999

"Scott G. Akmentins-Taylor" <staylor_at_mrynet.com> wrote:
> FYI Chuck, my MV IIs are quite happy using only the transmit, receive
> and ground when connected directly to my PCs. This is simply:
>
> MV II PC
> 2 ----------- 2
> 3 ----------- 3
> 7 ----------- 7

I don't see how that could work (reliably). If that's for a 25-pin PC serial
port, you've got 2 and 3 swapped. If it's for a 9 pin PC/AT style port,
ground needs to be on pin 5 rather than 7. In the latter case, I can imagine
that things might sort of work as long as the PC is driving RTS negative, but
I wouldn't want to count on that.


           25-pin 9-pin
Function DTE PC/AT uVAX
-------- ------ ----- ----
  TxD 2 3 2
  RxD 3 2 3
  RTS 4 7 4
  CTS 5 8
  DSR 6 6 6
  SG 7 5 7
  CD 8 1
  DTR 20 4 5
  RI 22 9

Since both PCs and uVAXes are DTE, the TxD and RxD lines between the two
need to be swapped (as do some handshake lines) to form a null modem.
Received on Wed Dec 15 1999 - 03:01:24 GMT