On 6/11/20 3:15 PM, Mattis Lind wrote:
The T11 is not halted - it's looping endlessly in the first ROM. There
is a brief burst of DRAM select activity on the scope just before it
hangs in the loop.
That burst of DRAM activity might indicate a DRAM problem. One thing
I have tried in the past is to put a known good DRAM on top of one
DRAM is the array. So to say in parallel. In the cases I have tried I
managed to make systems pass the memory check. Then test each and
every one in the DRAM array in the same way. Might be worth a try.
<snip>
The 2681 https://www.nxp.com/docs/en/data-sheet/SCC2681.pdf shouldn't
be to difficult to configure and is located on the same bus as the
keyboard so you should be able to send something on the UART to
either the printer/aux or the host.
========
Thanks again. I have some 4116's on order too. I'll try the piggyback
trick, and if it works, will desolder the offending RAM (and install a
machined-pin socket!) I will probably never have to change it again -
but the PC board wouldn't like another desolder operation...
If that doesn't work, then I'll start writing diagnostic software using
the 2681. Of course then I have to debug the program before I can debug
the terminal ;)
