Detailed reference for the DECF instruction in PIC18 ISA.
Decrement the contents of file register f by 1.
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
DECF 0x20, 0, 0 ; W = 0x20-1; d=0, a=0 → result in WREG, Access bank
DECF 0x20, 0, 0 ; W = 0x20-1; d=0, a=1 → result in WREG, Banked address
DECF 0x20, 0, 1 ; W = 0x20-1; d=0, a=1 → result in WREG, Banked address
DECF 0x20, 0, 1 ; W = 0x20-1; d=1, a=0 → result back to file register, Access bank
DECF 0x20, 1, 0 ; 0x20 = 0x20-1; d=1, a=0 → result back to file register, Access bank
DECF 0x20, 1, 0 ; 0x20 = 0x20-1; d=1, a=1 → result back to file register, Banked address
DECF 0x20, 1, 1 ; 0x20 = 0x20-1; d=1, a=1 → result back to file register, Banked address
DECF 0x20, 1, 1 ; 0x20 = 0x20-1; Pre-load WREG with literal, decrement f, result in WREG (Access bank)
MOVLW 0x10
DECF 0x20, 0, 0 ; W = 0x20-1; Pre-load WREG with literal, decrement f, result in WREG (Access bank)
MOVLW 0x10
DECF 0x20, 0, 0 ; W = 0x20-1