Dmitry Kiryashov says:
You can't apply sb/snb operations to [the W register ]. You need to put W value to some temp location first and finally check temp with sb / snb commands. [ed: unless you have optionx_carryx (or optionx on the old parts) in your device directive and have the RTW bit 7 of the option register cleared, then register 1 becomes the W register rather than the RTCC. The RTCC continues to work, but can't be read untill that bit is set. This is specific to the SX line of processors]
- and W, #$80 ; will test bit .7 in W, other bits are cleared ;-) and W, #$40 ; test bit .6 ;...
result of operation in Z flag (=0 means bit=1 otherwise bit=0 result to Z=1)
and W, #$xx is destructive command. You cannot restore W if you didn't save it before.
- 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.xor W, #A_CONST snb Z jmp A_CONST_MATCH xor W, #B_CONST^A_CONST ;compare with B_CONST snb Z jmp B_CONST_MATCH xor W, #C_CONST^B_CONST ;compare with C_CONST ;.... xor W, #LAST_CONST ;last used const value -> restore initial W ;.....
|file: /Techref/scenix/lib/math/bit/testbitsw_sx.htm, 1KB, , updated: 2004/6/10 13:40, local time: 2023/2/7 04:03,
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<A HREF="http://www.massmind.org/Techref/scenix/lib/math/bit/testbitsw_sx.htm"> PIC Microcontroller Bit Math Method Testing bits in W</A>
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