From: Iain Barker (ibarker@aastra.com)
Date: Tue Jul 29 2003 - 08:51:24 EDT
Various suggestions included slaving the serial printer off the VT terminal,
and a caution that running high-speed serial on two pairs within the same
connector isn't really what the secondary port was intended for (the RS232
spec says it is for low-speed modem management traffic).
Thanks in particular to Stan Horowitz and Peter Reynolds for their replies,
and suggestion of a third party cable vendor. In this case the easiest
solution turns out to be an off the shelf cable from, of all people, Sun
microsystems.
It seems that the weird legacy PDP/VAX scheme of multiplexing serial
terminals which we are trying to replace, was also used later by Sun for
their SPARC servers in order to split primary and secondary console serial
ports from a single DB25.
The Sun part number for the serial port splitter cable is X985Q / 530-1667
and generic copies appear to be readily available from KVM and other cable
vendors. With some DB25 to MMJ adaptors we should be all set.
Thanks once again to this great list for a speedy solution to a rather
arcane problem!
-----Original Message-----
From: Iain Barker
Sent: Monday, 28 July, 2003 18:55
To: tru64-unix-managers@ornl.gov
Subject: RS232 DB25 to dual MMJ cable (clarification)
Sorry, I should have been more explicit in the description here.
The RS232 standard includes one primary serial connection on pins 2,3
It also includes a secondary serial connection on pins 14,16
These are independent serial lines, as far as I am aware.
The cable we need has to support full RS232 DB25 connection. i.e. more than
just the primary TX+RX pins wires, it specifically has to include the
secondary TX and secondary RX pins wired to another serial line.
In our application one pair (the main, on pins 2,3) is being used for serial
terminal. The other pair (the secondary, on pins 14,16) is being used for a
serial printer.
What is required is a cable or adapter which can split the single DB25
connector into two separate RS232 MMJ (or DB9 etc) connections so that they
can go to independent ports on the VT520, which is replacing the aged VT100
plus printer.
i.e.
MMJ1 to RS232 25D-F (primary connection)
2 TX to pin 2 TX1
5 RX to pin 3 RX1
3+4 SG to pin 7 SG
MMJ2 to the same 25D-F (secondary connection)
2 TX to pin 14 TX2
5 RX to pin 16 RX2
3+4 SG to pin 7 SG
Does anyone have an idea for a supplier of this type of RS232 splitter
cable?
I need a quantity of these, otherwise I would just solder one up myself.
thanks.
ps. apologies for the double posting.
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