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From: rhyde@ucrmath.ucr.edu (randy hyde)
Newsgroups: comp.sys.nsc.32k
Subject: Re:  ICU and the Refresh Clock
Message-ID: <13076@ucrmath.ucr.edu>
Date: 27 Mar 91 05:07:11 GMT
References: <9103251713.AA00711@hplwbc.hpl.hp.com>
Organization: University of California, Riverside
Lines: 41

>>>>>
> I copied the instruction sequence from Bruce's monitor *exactly* (the one
> which initializes the ICU to generate the refresh clock) and executed it from
> RAM under control of the monitor.  It crashed the system.

Did you execute the code which initializes the memory parity?  It
writes every location in the DRAM, which would have wiped out your
program.  When I debugged the monitor, I also ran it in DRAM.
However, I inserted a "br _main" at the beginning so it would skip
the memory initialization.
<<<<<

It turned out to be one of those very stupid mistakes you're always
so embarrassed to admit to.  I copied your code *exactly*.  Part of the
sequence was to write an x'ff to the 32202 output port.  This swapped out
RAM and swapped in EPROM at address zero.  You're code worked because the
same data appeared at the same locations in RAM and EPROM, mine died because
once the EPROM got swapped in, who knows what was happening at address 30000h?

I now have some conditional assembly directives which assemble the code two
ways, one for debugging in RAM, one for EPROM.  Both work like a charm at this
point.

I wrote my own debugger/monitor about eight years ago (for the 16032).  I've
just managed to port it to the PC532 and I'm enhancing it to take advantage of
the 32532.

The direct exception mode on the 32532 is *great*.  I always  hated the fact that
programs *had* to have MOD table entries to restore the SB value.  With the
DE mode I can treat SB like any other register (i.e., when saving and restoring)
within the debugger.

Hopefully I will be able to contribute some code to this project in the near
future.  For those still debugging their boards, my startup code is performing
various diagnostic tests and display the results on the LEDs.  This makes
bringing up systems a little easier.  As soon as I can figure out all kinds
of useful diagnostics, I may design an EPROM specifically for bringing up
PC532 motherboards.

Oh well, back to the debugger.
*** RAndy Hyde