On Wed, 14 Jan 1998 13:49:51 +1300, you wrote:

>well, yes, but most mortals want to subtract literal x from the value y
>in the accumulator, not the other way round, and to be honest I've never
>seen another microcontroller with such a strange instruction.
doesn't mean it's not a good thing - skip instructions were also not
that common until recently

>it allegedly has a use, but what that is I can't remember. You end up
>doing addlw -20 which hardly helps readability.
OK, then write a 'subwl' macro then! 

If they'd done it the other way round, it would be a waste of  silicon
as you can acheive the same thing using addlw. Having a literal - W
function provides extra functionality. I find it useful for doing 2's
complements with sublw 0 - very handy for finding absolute values : 

movlw a
subwf b
skpc
sublw 0

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