PIC18 cheatsheet
ADDWFADDWFCANDWFCLRFCOMFCPFSEQCPFSGTCPFSLTDECFDECFSZDCFSNZINCFINCFSZINFSNZIORWFMOVFMOVFFMOVWFMULWFNEGFRLCFRLNCFRRCFRRNCFSETFSUBFWBSUBWFSUBWFBSWAPFTSTFSZXORWF
BCFBSFBTFSCBTFSSBTG
BCBNBNCBNNBNOVBNZBOVBRABZCALLCLRWDTDAWGOTONOPPOPPUSHRCALLRESETRETFIERETLWRETURNSLEEP
ADDLWANDLWIORLWLFSRMOVLBMOVLWMULLWRETLWSUBLWXORLW
TBLRD*TBLRD*+TBLRD*-TBLRD+*TBLWT*TBLWT*+TBLWT*-TBLWT+*

SUBLW

Detailed reference for the SUBLW instruction in PIC18 ISA.

Description

Subtract the contents of WREG from an 8‑bit literal constant k. The result is written back to WREG.

  • Operation: WREG = k - WREG.
  • Status bits (C, Z, DC, OV) are updated as with any 8‑bit subtraction. The result is always stored to WREG regardless of flags.

Examples

; From literal, WREG=5, literal=10 → W=5
MOVLW 0x05
SUBLW 0x0A
; Underflow, WREG=2, literal=0 → W=0xFE
MOVLW 0x02
SUBLW 0x00
; Borrow across the high byte, WREG=0xFF, literal=0x80 → W=0x81
MOVLW 0xFF
SUBLW 0x80
; Zero result, WREG=0, literal=0 → W=0
MOVLW 0x00
SUBLW 0x00
; Literal pre‑load then subtract, result in W
MOVLW 0x12
SUBLW 0x20   ; W = 0x20 - 0x12 = 0x0E