[sdiy] Prophet 5 Q & which z80?

[Paul Wagorn]

thanks phillip - actually, the mux was replaced, so it's working properly.
it seems as though the mux isn't getting a clock signal...
paul

-----Original Message-----
From: phillip m gallo [mailto:philgallo at attglobal.net]
Sent: Wednesday, June 25, 2003 4:34 PM
To: Paul Wagorn
Subject: RE: [sdiy] Prophet 5 Q & which z80?


Paul,

The z80 uses external ROM for program store and external RAM for data store
(disregarding any additional circuitry such as MUX's).

If the Z80 never demonstrates (directly at the chip) any activity on the
lower 3 address lines then you have found the "symptom" of a fundimental
problem that would keep the CPU from executing the control program properly.

This symptom does not, however, indict the Z80 particularly based upon this
form of observation.

I would start by investigating the locations these lines terminate and
wouldn't indict the ROM/RAM at first blush.  I would focus on other
peripheral connections (like MUX's, Buffers, etc).

Also if the part is socketed; 1) pull the part; 2)lift the low address pins;
3)place the device back in the socket; 4)monitor these lines for activity.
If they wiggle you know the Z80 is ok (but don't expect proper device
operation).  Now re-seat the pins and look at the peripheral connection to
the low address lines.

regards,
p

---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.491 / Virus Database: 290 - Release Date: 6/18/03