Subject:
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Pattern in RCX opcodes.
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Newsgroups:
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lugnet.robotics
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Date:
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Sun, 20 Dec 1998 16:20:05 GMT
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Original-From:
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Vadim Strizhevsky <VADIM@avoidspamOPTONLINE.NET>
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Viewed:
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1152 times
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Did anyone notice that the last hex digit of the RCX opcodes uniquely (well
almost) identifies number of bytes that the opcode takes as arguments?
0,6 -> void
1,7 -> 1 byte
2 -> 2 bytes.
3 -> 3 bytes.
4 -> 4 bytes.
5 -> 5 bytes
I think the only exceptions are 0x95 and 0x45, but I might have missed
something.
This is probably from the ream of neat-but-useless information, but being a
number theory fan I couldn't help but notice it. It definately looks "by
design", so I wonder if this is somehow used in firmware or ROM?
-Vadim
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Message has 1 Reply:
 | | Re: Pattern in RCX opcodes.
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| (...) This is certainly used by the ROM. I believe Paul Haas was the first to notice this, see the comment on my web page, (URL) notes Paul Haas was right about messages being grouped and parsed by lower 3 bits And lower, in the RXI handler: receive (...) (26 years ago, 20-Dec-98, to lugnet.robotics)
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