On Fri, 27 Jul 2007 14:58:28 +0100, Matthew Rhys-Roberts wrote:

> As far as I can see, there's no built-in MOVLF (move literal to file) 
> instruction, at least on the 18F6680 I've been working on.
> 
> I know it's hardly a problem to load the literal into W first, then move 
> W into the desired file, but why would they fail to design such a useful 
> one-step function?

Well historically, there wasn't room.  With a "mid-range" 14 bit instruction, 8 bits are needed for the literal, leaving only 6 for the opcode and the 
destination address.  Even if they used just one bit for the opcode (really wasteful, as it would take up half of the instruction "space" available for 
this one instruction) it would only leave 5 bits, or 32 addresses for the deatination - next to useless.

Why they didn't introduce it with the 18 series I don't know, but I presume there's a reason deep in the design philosophy!  :-)

Cheers,


Howard Winter
St.Albans, England


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