[Info-vax] DEC3000->DECServer90TL->CMM comunication problem

[John E. Malmberg]

On 4/18/2013 4:16 PM, Steven Schweda wrote:
>> - we tried to connect a PC with WinXP to the DECServer ports
>> through RS232 and "listen" on the Hyperterminal software to
>> the ports (setting appropriate transmission parameters) but
>> without any success. On the other hand, we are not sure about
>> the wiring between the RJ45 -> RS323 (9 pins).
>
>     Sounds reasonable, if you could trust your cable.
>
>     I normally use null-modem cables with 25-pin connectors,
> and then 25-pin-to-9-pin adapters when I want to connect to a
> 9-pin serial port on a computer.  The result seems to be as
> follows (which will look better with a fixed-width font):
>
>                    DS90TL port (F)
>
>      i     i     o     -     o     o     o     i      in/out
>      1     2     3     4     5     6     7     8
>     Rgnd  RXD   Tgnd  CTS   RTS   TXD   DTR   DSR
>                 Gnd   (nc)   +-----------+
>
>     ---------------------____--------------------
>
>
>        D-9 (F)
>     5  4  3  2  1
>      9  8  7  6
>
>
>           DCE   DS90
>           D9F    RJ
>     +-- DCD 1 - 8 DSR
>     |   TXD 2 - 6 TXD
>     |   RXD 3 - 2 RXD
>     |   DSR 4 - 7 DTR ----+
>     |   GND 5 - 1 Rgnd    |
>     |           3 Tgnd    |
>     +-- DTR 6 - 8 DSR     |
>         CTS 7 - 5 RTS ----+
>         RTS 8 - 4 CTS
>         RI  9 - nc
>
>     Pins 1 and 6 of the D-9 connector are joined in my
> (null-modem) cable.  Pins 5 and 7 of the DS90 are joined by
> the DS90.  I don't claim that it's all correct, but it seems
> to work here, so it should be adequate for your testing.

Pin 5 of the DCE needs to be connected to both the "Rgnd" and "Tgnd" on 
the RJ port unless you are absolutely certain they are connected 
internally on DS90.  In which case the cable is specific to that 
equipment and not generic.

Otherwise you can have strange and sometimes hard to find intermittent 
data issues.

This is how a site discovered that the ground prong on the power cord 
was not connected well on a surge suppressor.  Because the both the *gnd 
lines were not connected, one of the data signals return was actually 
through the safety ground, but only if you did not bump the suppressor 
too hard.

Regards,
-John
wb8tyw at qsl.network
Personal Opinion Only