11 Jun
2020
11 Jun
'20
2:30 p.m.
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 ;)