Dmitry Kiryashov says:
You can't apply btfss/btfsc operations to [the W register]. You need to put W value to some temp location first and finally check temp with btfss/btfsc commands.HINTS:
ANDLW 0x80 ; will test bit .7 in W, other bits are cleared ;-) ANDLW 0x40 ; test bit .6 ;...result of operation in _Z flag (=0 means bit=1 otherwise bit=0 result to _Z=1)
ANDLW is destructive command. You cannot restore W if you didn't save it before.
ADDLW 0x88 ; will test bits .7 and .3results of operation in _C and _DC flags. To restore initial W just ADDLW -0x88 ;-)
- You can also apply XORLW value command to check identity W to some value. It is useful command (sometimes) 'cause you can do comparison for alot of values and restore W after that to initial value.
XORLW A_CONST SKPNZ GOTO A_CONST_MATCH XORLW B_CONST^A_CONST ;compare with B_CONST SKPNZ GOTO B_CONST_MATCH XORLW C_CONST^B_CONST ;compare with C_CONST ;.... XORLW LAST_CONST ;last used const value -> restore initial W ;.....
file: /Techref/scenix/lib/math/bit/testbitsw.htm, 1KB, , updated: 2004/6/10 13:40, local time: 2024/12/22 22:03,
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