; during send data...
TRANSMIT:
; ...
    MOV A,#DATA_TO_BE_SENT ; 7 bit of data to be sent
    MOV C,P                ; catch parity bit
    MOV ACC.7,C            ; place it as 8th bit
    MOV SBUF,A             ; send to receiver
; ...

; during receive data...
RECEIVE:
; ...
    MOV A,SBUF             ; get 7 data bits + parity bit
    JB P,RECEIVE_ERROR     ; parity mismatch
; ...