From: Brian Ketterling (tweel8502_at_hotmail.com)
Date: 2003-11-06 01:18:57
Just 2 cents...
>From: Steve Judd <sjudd@ffd2.com>
>
>Yes, it is actually a two-byte opcode -- the PC counter goes to PC+2.
>But nothing is actually done with the second byte; if it were e.g. pushed
>onto the stack it might have been useful as a software interrupt...
>
>...Sorry to follow-up on my own message, but I forgot to mention that the
>WDC
>65816 data sheets call out BRK as two bytes -- "officially", it's
>documented as a 2-byte opcode.
I'm away from my 65816 docs, so I'm not sure, but I *think* on that MPU it
is possible to pass the second byte as a parameter.
>From: "Gideon Zweijtzer" <gideonz@dds.nl>
>
>Of course, only the design team of the 6502 knows for sure what the
>reason is...
I think the design team was one or maybe two guys, working primarily on
paper.
>...The size of a 6502
>instruction is easily derived from the opcode by the following formula:..
That's pretty clever!
-- Brian
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