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Old 14th Oct 2018, 7:27 pm   #35
buggies's Avatar
Join Date: Jan 2009
Location: West Lothian, UK.
Posts: 357
Default Re: 486 PC. Keyboard problem.

Originally Posted by Station X View Post

I had another play this afternoon. At this stage I just want to prove that the serial ports are working before I attempt to connect to the machine.

At start up the BIOS shows three com ports with addresses $3F8, $2F8 and $3E8.

Entering "mode" at the DOS prompt was a dismal failure, possibly due to the fact I can't find a way of pausing the display before it scrolls off the screen. I couldn't find a way of generating the pipe character | from the keyboard I was using.

Entering "mode com1/status" at the prompt returns "RETRY=NONE". Same for com2 and com3.

I configured com port 1 using "mode com1:9600,N,8,1,P. Did the same for com2 and com3. Got responses showing ports had been configured.

mode com1/status now returns "RETRY=B" Same for com2 and com3.

Entering "echo 1234567890 > com1" at the prompt returns "invalid device request writing com1". Same for com2 and com3.

I assume I have a hardware problem with the com ports?
Mode > fred.txt to create a text file if there is an editor on the machine.

I have forgotten most of this stuff but a quick look at a web site reminds that the retry is just what to do on timeout - but I think you should have got more info returned than just that.

Probably copy config.sys com1: would give the same invalid device error as the echo command. Any possibility the ports need RTS-CTS linked or special drivers for the ISA card (hopefully not).

Google found a similar but unresolved fault here:-
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