Hi,
Let's not mix reset with interrupt, OK?
RESETb on the 8048 is an active low signal that puts the CPU in
a known condition, ready to start executing code once the signal
is released. It is a low level to reset the CPU, and high to let it run.
Pretty much all CPU's need a reset signal to put them into a known
state at power up (although some generate the signal internally).
If you don't have a storage scope, it will be hard to see that reset is
low when you power up. Mainly you are just checking to see that it's
high normally, to let the CPU run.
In general, RESETb would be asserted for a long enough time to
let the crystal oscillator start up, and the 5V power stabilize. The oscillator
would only take a few mS to get going, typically, but reset is often asserted
for maybe 100-200 mSec, since all that does is make the start-up take a little
longer and you want to make sure the CPU is reset properly.
Bob
--------------------------------------------
On Sun, 2/7/16, jw_dewdney@yahoo.com [PolySix] <PolySix@yahoogroups.com> wrote:
Subject: Re: [PolySix] Re: The Post I didn't want to make....
To: PolySix@yahoogroups.com
Date: Sunday, February 7, 2016, 1:31 PM
thanks for the suggestions Bob! no... i used the
22pf cap on the materials list... i came across the post
about the 10pf replacement just yesterday in fact. the one
thats supposed to be 10pf measured closer to 3pf... though
its pretty hard to get an accurate fix on values in the low
pf range even with really good equipment as you know. i
think ill order some 10pf caps and do some replacing on the
board.
i asked if this
was some kind of 'normal condition' because someone
just below in a post who just did the same board swap just
mentioned something cryptic about loading factory programs
and how now 'more of the lights seem to be going
away'... or something to that effect... perhaps i should
ask him...!
also... is
there a FAQ somewhere here on relevant problems? or
something from Jed on 'startup procedures' and
troubleshooting? im having a bit of a hard time getting
relevant search results in this group. as for the reset pin
on the processor... what kind of input does in need to start
the interrupt? short to ground? guess i should read the
manual for that processor...
i could also try swapping processors
i guess (have two more p6s to do!... hope i can get one of
em right!!). id have tried the board in one of the other p6s
though it really looks as though the problem is coming from
the new board...
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