At 21:58 24.03.97 -0600, you wrote:
>> > > Puzzle N2>   Is required to load any file REGister with value = VALUE ,
>> > > but W register haven't be changed after load is over .
>> >
>> > MOVWF reg
>> > XORLW VALUE
>> > XORWF reg,f
>> > XORWF reg,W
>> I've another similar solution...
>>
>> XORLW VALUE
>> MOVWF REG
>> XORLW VALUE
>> XORWF REG,F
>
>Depending upon /Value/, it may be possible to do the job in 1 to 5 cycles
>without altering W _or_ the flags (useful perhaps in an ISR, since saving
>context is such a pain).  If the old value in the f-register is known, then
>any change may be done in 0 to 4 cycles (zero of course being if you want to
>"change" the register to its existing value).
>
>Here are some of the ways of setting a register in very few instructions:
>
>[1] Set to zero: the obvious one...
>        clrf    reg

Doesn't CLRF alter the Z-flag?!

>
>[2] Set to a power of two.  Also pretty obvious...
>        clrf    reg
>        bsf     reg,bit
>
>[3] Set to 255.  Still pretty obvious, but for one slight detail...
>        clrf    reg
>        decfsz  reg     ; Note: next instruction will NEVER be skipped.

Don't we have SETF reg ? (Perhaps only 17Cxxx)

regards,

Wolfram



+-----------------------------------------------------+
| Wolfram Liebchen                                    |
| Forschungsinstitut fŸr Optik, TŸbingen, Deutschland |
| mailto:liebchen@ffo.fgan.de                         |
+-----------------------------------------------------+