Detailed reference for the SUBWF instruction in PIC18 ISA.
Subtract the contents of WREG from file register f.
d = 0 → result is stored in WREG.d = 1 → result is stored back into register f.a = 0 → Access‑bank addressing.a = 1 → Banked addressing.; d=0, a=0 → result in WREG, Access bank
SUBWF 0x20, 0, 0 ; W = 0x20 - W; d=0, a=0 → result in WREG, Access bank
SUBWF 0x20, 0, 0 ; W = 0x20 - W; d=0, a=1 → result in WREG, Banked address
SUBWF 0x20, 0, 1 ; W = 0x20 - W; d=0, a=1 → result in WREG, Banked address
SUBWF 0x20, 0, 1 ; W = 0x20 - W; d=1, a=0 → result back to file register, Access bank
SUBWF 0x20, 1, 0 ; 0x20 = 0x20 - W; d=1, a=0 → result back to file register, Access bank
SUBWF 0x20, 1, 0 ; 0x20 = 0x20 - W; d=1, a=1 → result back to file register, Banked address
SUBWF 0x20, 1, 1 ; 0x20 = 0x20 - W; d=1, a=1 → result back to file register, Banked address
SUBWF 0x20, 1, 1 ; 0x20 = 0x20 - W; Load literal into WREG then subtract, result in WREG (Access bank)
MOVLW 0x05
SUBWF 0x20, 0, 0 ; W = 0x20 - 0x05; Load literal into WREG then subtract, result in WREG (Access bank)
MOVLW 0x05
SUBWF 0x20, 0, 0 ; W = 0x20 - 0x05