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From: FTPAM1@ALASKA.BITNET
Newsgroups: comp.sys.atari.st
Subject: If your data rates are not excessive, you can write out
Message-ID: <9001170805.AA27127@ucbvax.Berkeley.EDU>
Date: 16 Jan 90 21:31:43 GMT
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Reply-To: <FTPAM1%ALASKA.BITNET@CUNYVM.CUNY.EDU>
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data serially, using one address line for the write enable
signal and another for a single data bit.  This is how the
SmartWatch clock/calendar sockets work.

     If you have enough address lines available, you could
write out nibbles or whole bytes the same way.  If you call
the lower 8 address lines your write data bus and A8 your
write signal, you could transmit bytes to your external
circuit by reading from addresses xx100H to xx1FFH.

     I have an microprocessor in circuit emulator that uses
this technique to get at internal CPU information through a
ROM socket.  Its data rate is very slow, suitable only for
single stepping and not real time emulation.  The emulator
can, however monitor bus traffic in real time.  So when I
need to examine a specific register in real time I insert a
subroutine to read from FFxxH to signal the regiser
contents.

Philip Munts, N7AHL
University of Alaska, Fairbanks
FTPAM1@ALASKA