John Orhan wrote: > Could I ask what the intruction 'SKPNC' does? Is it skip if not > carry? Forgive my ignorance but I have not seen it before. John: Yeah, it means "skip if the carry flag is clear"; it's equivalent to BTFSC STATUS,C and it's always been supported by MPASM, although it hasn't always been documented. The latest MPASM/MPLAB User's Guides contain a table showing this and all other pseudo-ops understood by MPASM; here's the list: PIC16CXX SPECIAL INSTRUCTION MNEMONICS Name Mnemonic Equivalent Status Operation(s) Clear Carry CLRC BCF 3,0 - Clear Digit Carry CLRDC BCF 3,1 - Set Digit Carry SETDC BSF 3,1 - Clear Zero CLRZ BCF 3,2 - Set Zero SETZ BSF 3,2 - Skip on Carry SKPC BTFSS 3,0 - Skip on No Carry SKPNC BTFSC 3,0 - Skip on Digit Carry SKPDC BTFSS 3,1 - Skip on No Digit Carry SKPNDC BTFSC 3,1 - Skip on Zero SKPZ BTFSS 3,2 - Skip on Non Zero SKPNZ BTFSC 3,2 - Test File TSTF f MOVF f,1 Z Move File to W MOVFW f MOVF f,0 Z Negate File NEGF f,d COMF f,1 INCF f,d Z Add Carry to File ADDCF f,d BTFSC 3,0 INCF f,d Z Subtract Carry from File SUBCF f,d BTFSC 3,0 DECF f,d Z Add Digit Carry to File ADDDCF f,d BTFSC 3,1 INCF f,d Z Subtract Digit SUBDCF f,d BTFSC 3,1 Carry from File DECF f,d Z Branch B k GOTO k - Branch on Carry BC k BTFSC 3,0 GOTO k - Branch on No Carry BNC k BTFSS 3,0 GOTO k - Branch on Digit Carry BDC k BTFSC 3,1 GOTO k - Branch on No Digit Carry BNDC k BTFSS 3,1 GOTO k - Branch on Zero BZ k BTFSC 3,2 GOTO k - Branch on Non Zero BNZ k BTFSS 3,2 GOTO k - Call across page boundary LCALL k BCF 3,5 or BSF 3,5 BCF 3,6 or BSF 3,6 CALL k By the way, don't bother using the "LCALL" pseudo-op... Since it doesn't restore the code-page bits after the CALL, it's sorta useless. Also, be careful with the pseudo-ops that assemble to two instructions; constructs like the following, for instance, will cause you great pain and suffering: ; DON'T DO THIS! BTFSS FLAGS,SWITCH ;If the switch is pressed, skip ahead. NEGF REG ;Otherwise, negate the REG register. -Andy === Andrew Warren - fastfwd@ix.netcom.com === Fast Forward Engineering - San Diego, California === http://www.geocities.com/SiliconValley/2499