help - 11/34 console problem - first measurement results
henk.gooijen at oce.com
Sun Nov 6 02:20:27 CST 2005
> Interesting, the LSB is being lost somewhere (that would explain why
> 1 does nothing, why 5 behaves as 4, etc).
> What sort of RAM is on this board (I can't be bothered to find the
> prints tonight ;-)), do you know if it's good. I've found old SRAM
> to be notoriously unreliable.
Interesting, I had not thought of that, may be a stuck bit.
I must have a better look at the program code listing. Checking out
the RAM is a bit difficult. It consists of two 4-bit chips with
separate data IN and data OUT pins, type 86586 (?).
If the 8008 uses the RAM for storage of variables, I guess that I can
safely say that the RAM (plus associated circuitry to read/write) must
> Since I have a logic analyser 'to hand', I would start looking at those
> 3 inputs to the '47. Where do they come from on the M7859? An output
> port on the 8008? Do we know that port is latching correctly? Or more
> likely, the 8008 is writing the wrong values to it.
Page KY-4 has all the decode logic. There is a second post to this list
on its way, posted Friday morning ... it's now Sunday morning ...
The signal KY4 READ INPUT 5L from the 74154 is used on page KY-3 to
enable 8093 AND gates to read the scan matrix lines.
The signal KY4 LD REG 0H via a 7404 from the 74154 is used on page KY-6
to enable a 74175 latch of which the outputs drive the scan matrix.
Likewise, KY4 LD REG 1H drives the 3 NUM lines for the 7447.
Before I go on writing long stories here, I think it is best to wait
for the e-mail from last Friday to appear here.
Thanks for working with me Tony, it helps keeping focussed ...
- Henk, PA8PDP.
This message and attachment(s) are intended solely for the use of the addressee and may contain information that is privileged, confidential or otherwise exempt from disclosure under applicable law.
If you are not the intended recipient or agent thereof responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited.
If you have received this communication in error, please notify the sender immediately by telephone and with a "reply" message.
Thank you for your cooperation.
More information about the cctech