[ltp] IBM 600E, RH9, minicom problem

[Heiko Rosemann]

Hi,

On Fri, 27 Feb 2004, Bill Voight wrote:

> Sports fans,
>
> IBM 600E, RH9, minicom serial port  Setup- /dev/ttyS0 9600 8N1, Hardware
> flow control, no Software Flow Control
>
> I'm using settings identical to those I've been using on several other
> RH boxes to connect to the A serial port of some U2's.  I am using a
> known good null modem cable and gender bender to connect.  Works fine on
> the desktops, no dice on the IBM 600e.  I've run the diags from the
> 600E's bios- they show everything's OK.  Have had no luck with docs- I
> haven't found anything indicating there's anything different about the
> serial port on a 600E.  Setserial output from both is listed below- it's
> identical.  Anybody got any ideas?

I recall there have been a few problems with laptops who do not deliver the
standard +15V/-15V RS232-signals, but lower voltages (+7V/-7V is a number I
seem to recall) So if you have some access to a scope, it might be worth
measuring the voltages on the port pins. Most serial devices work with
signals that low, but some refuse.

Another possibility: Quite a few serial devices draw power from the port
(more specifically the handshake lines) I don't know what a "U2" is, so I'm
just guessing here, but it could be that it is exceeding the RS232 specs in
terms of current draw, so it won't work with the maybe more spec-conformant
laptop port.

Do you have any other device to test the port with? What happens if you just
connect RXD and TXD (pins 2 and 3 on the 9pin-connector) and try
transmitting without any flow control?

HTH, Heiko
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