Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!apple!altos!gumby!steve
From: steve@gumby.Altos.COM (Steve Scherf)
Newsgroups: comp.sys.handhelds
Subject: Chip 48 v2.25 question
Message-ID: <4741@gumby.Altos.COM>
Date: 28 Mar 91 22:26:42 GMT
Reply-To: steve@altos.COM (Steve Scherf)
Organization: Altos Computer Systems, San Jose, CA
Lines: 24

I have an esoteric question about two instructions in the Chip48 machine
code. If this has already been discussed here, please bear with me as I
have not been reading this group for the past 4 or 5 months.

In the original document from gson@niksula.hut.fi there is a one-line
description of each of the instructions and their opcodes. Two in particular
are described ambiguously; these are the instruction to do a left shift one bit
and the analogous instruction to do a right shift. The documentation states
that the opcode for a right shift of register VX is 8XY6 where X is the
hex digit after the 'V' in VX. That's all fine and dandy, but what's 'Y'?
This is a single register operation, so why is there a 'Y' in the opcode?
Similarly, the left shift opcode is 8XYE with no obvious reason for a 'Y'.

Also, not actually having written a chip 48 program yet, can anyone tell me
what the byte ordering for a two byte instruction is? Is it big-endian like
sprites?

Thanks!

-- 
Steve Scherf
steve@Altos.COM    ...!{sun|sco|pyramid|amdahl|uunet}!altos!steve

These opinions are solely mine, but others may share them if they like.