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From: jlw@io.UUCP
Newsgroups: comp.sys.m6809
Subject: Re: 512K and wimpy GIME chips
Message-ID: <220@io.UUCP>
Date: Wed, 18-Feb-87 16:37:12 EST
Article-I.D.: io.220
Posted: Wed Feb 18 16:37:12 1987
Date-Received: Fri, 20-Feb-87 00:53:05 EST
References: <1404@ihwpt.UUCP>
Organization: AT&T IS Labs, Middletown NJ USA
Lines: 15


One problem you might be running into is a peculiarity
of the WECo 256K DRAM.  256K DRAMs have A0-A8 strobed
twice with CAS and RAS respectively.  Since the architecture
of a 256K chip is really a 4x64K only A0-A7 are active
for refreshing.  If your board design tri-states A8
of a WECo. 256K DRAM during refresh, your data will die.
The real problem is that this is very hard to determine
with standard memory check programs since they
access the memory often enough to keep it refreshed.
Then when you try to run real code.....boom...Panic Trap.


Joe Wood
io!jlw