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Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!ihnp4!inuxc!pur-ee!uiucdcs!trsvax!mikey
From: mikey@trsvax.UUCP
Newsgroups: net.micro
Subject: Re: TRS80 Model 16A Help - (nf)
Message-ID: <53400038@trsvax.UUCP>
Date: Tue, 19-Jun-84 18:28:00 EDT
Article-I.D.: trsvax.53400038
Posted: Tue Jun 19 18:28:00 1984
Date-Received: Sat, 23-Jun-84 03:12:24 EDT
References: <2173@mit-eddi.UUCP>
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Nf-ID: #R:mit-eddi:-217300:trsvax:53400038:000:1043
Nf-From: trsvax!mikey    Jun 19 17:28:00 1984

#R:mit-eddi:-217300:trsvax:53400038:000:1043
trsvax!mikey    Jun 19 17:28:00 1984




There are no ports common to the Z80 and the 68000 in the model 16.  There
is a shared 16k window of RAM that is switched in on the Z80 side at address
8000h - BFFFh and is definable on the 68K side.  On the Model 16, status
is sent by setting flags in memory in the window.  All this information is
in the copy of the Model 16 service manual that was published, (at least in
my copy) but if you were looking for a port, it is probably easy to overlook.

For communication, you must first switch out the bank of memory normally
at 8000-FFFF hex which is controlled at port FF and then use the memory control
port on the 68K card to switch in a 16k window of the 68K memory.  
Since this window is definable as to its location in the 68K memory, this is
also how you load your original 68K startup program.

If you're going to muck around, I suggest you do it from TRSDOS 2.0x, as 2.0
has no idea of the existance of the 68K or the extra RAM.  TRSDOS 4.x will try
use the 68K ram to put some I/O buffers and drivers there.

mikey at trsvax