help - 11/34 console problem - first measurement results - test-drb@ccmp.vtda.org

7 Nov 2005

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Subject: RE: help - 11/34 console problem - first measurement results
   From: "Gooijen, Henk" <henk.gooijen at oce.com>
   Date: Sun, 06 Nov 2005 18:06:41 +0100
     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
     Cc: "Gooijen, Henk" <henk.gooijen at oce.com>

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Allison wrote:
 =

  I'd consider that the 8008 is getting bad
input data from a bad scan line= 
  which it will output or that it's outputing
correctly and the data is
 corrupted after output due to bad latch or other hardware.

 One likely possibility is not ram as a prblem but a I/O port that has a
 stuck bit. Or the control for that port is stuck.  This is most likely
 if the basic fuctions are there (8008 program runs) but some parts of
 the data used to control the 11/34 or display it's status is not correct.= 

 FYI the 8008 can be single stepped if you pull the "READY" line each
 cycle and just look at the bus with a simple logic probe or clip. 
Thanks for the good input Allison!
I hooked a logic analyzer to the address lines A0-A7 on one of the program
ROMs, and simply sampled the data without any trigger. With the display in
octal mode, I can see the executed address sequence. The 8008 executes the
main loop and calls SHFT1 *and* returns to the correct PC. That means that
the ROM, RAM (to store the return address) and associated circuits must be =
OK. 
Ok rom for sure and may be on the ram.  The 8008 has an internal push 
down stack that is 8 deep for call/return.

Allison