11 Nov
2018
11 Nov
'18
10:04 p.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Brent
Hilpert via cctalk
Sent: 11 November 2018 21:50
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Subject: Re: Another IC I Can't Identify
On 2018-Nov-11, at 1:32 PM, Rob Jarratt wrote:
Perhaps I'm not clear on what you're saying, I was taking you as meaning
you
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of
Brent Hilpert via cctalk
On 2018-Nov-11, at 11:52 AM, Rob Jarratt via cctalk wrote:
> Thanks for all the replies. If that is indeed what it is, then I
> still
have not
been able to find the source of one of the
signals that seems to be
causing
the Reset, every pin I have found so far is an
input, I have not
found it connected to the output of anything yet :-(
Have you tried the reverse? : follow an origin that you know should
be controlling reset, such as the power-on indication from the PS,
and see if
you
can trace it to the CPU.=
I have already found that source and it all looks OK. I think I have
identified another input to a NOR gate that is high and causing the
reset, but I can't find where it comes from.
hadn't found a source driving the reset line.
While you've found a PWR-OK signal and it looks good, have you found how
it connects to the reset line?
Reset-line arrangements on small machines aren't usually that complicated.
(Usually the power-on signal source is a series RC combination (often with
additional discretes such as diodes) between a power-bus and ground).
Perhaps put up an image of the schematic you have so far.
I have posted an image here:
https://rjarratt.files.wordpress.com/2018/11/system-board.png
At the far right you will see a "To F11 Reset", my understanding is that
this is active High. I have determined that the D input on E141 is always
high. The CLR input on E141 is periodically set, thus causing a pulsing high
output on E141, leading to a pulsing Reset on the F11 chipset.
Thanks
Rob
