Serial console problems on 11/34

[Julian Wolfe (FireflyST)]

Sorry, I shouldn't have renamed the topic so soon.  I fixed the problem - I forgot to jump pins E to M (interlock) - did that and I was able to input.

-----Original Message-----
>From: Tony Duell <ard at p850ug1.demon.co.uk>
>Sent: Jun 22, 2006 5:54 PM
>To: cctalk at classiccmp.org
>Subject: Re: Serial console problems on 11/34
>
>> 
>> I get the following prompt:
>> 
>> ###### ###### ###### ###### (where ###### is the register values)
>> $ 
>> 
>> It's just that I can't respond to it. "L" for example is not echoed on the
>> terminal when I press a key.
>
>OK, your machine is basically working. The CPU seems to be running the 
>console firmware, it can talk to the transmit half of the DL11. You've 
>also not used a straight-through RS232 cable -- the output of the PDP11 
>is certainly going to the input of the terminal.
>
>Here's how I'd attack this problem (being a hardware hacker...)
>
>1) Make sure the terminal is sending something. Put a breakout box 
>between the terminal and the PDP and press keys. Check you get some 
>indication on the breakout box LEDs that the TxD line from the terminal 
>is changing state.
>
>2) Grab the printset for the DL11 and look at the output of the buffer 
>chip (probably a 1489) that handles the RxD line. Put a logic probe on 
>the output of that buffer, again prsss keys on the terminal and chack 
>that pin changes state (if not, suspect the buffer chip, they do fail...)
>
>3) Now put the logic probe on the serial input pin of the UART and again 
>press keys. If there are no transitions here, maybe you've forgotten the 
>jumper wire in the cable connector that links the output of the RS232 
>receiver (or the current loop receiver) to the UART.
>
>4) If serial data is getting to the UART, maybe the Rx Clock is missing. 
>Look at the appropriate pin of the UART chip with the logic probe to 
>ensure it's clocking. If you have a 'scope, make sure the frequency is 
>right too (16 times the baud rate).
>
>-tony