;-=-=-=-=-=-=-= ; BITS_SEG SEGMENT BIT BUFF_SEG SEGMENT IDATA CODE_SEG SEGMENT CODE ; ;-=-=-=-=-=-=-= ; RSEG BITS_SEG RAW_BIT: DBIT 1 ; raw handling bit ; ;-=-=-=-=-=-=-= ; RSEG BUFF_SEG BIT_BUF: DS 32 ; raw bit buffer ; ;-=-=-=-=-=-=-= ; RSEG CODE_SEG ;-=-=-=-=-=-=-= ;NAME: GET_BIT ; Used to fetch a bit from the raw bit buffer ; into the BIT_RAW bit. Entry R0 is the bit number ; that is preserved. ;-=-=-=-=-=-=-= GET_BIT: MOV A, R0 ; save R0 on stack PUSH ACC ; save entry bit number ; RR A ; make byte offset number RR A RR A ANL A, #01FH ; mask the byte number ADD A, #BIT_BUF ; make pointer to byte MOV R0, A ; save buffer offset into R0 POP ACC ; get copy of bit number PUSH ACC ANL A, #007H ; isolate 0-7 number CALL BIT_MSK ; convert bit # to a mask ANL A, @R0 ; get current bit state JNZ GET_BIT1 ; for return of a 1 bit GET_BIT0: CLR RAW_BIT ; clear RAW_BIT for 0 bit state JMP GET_BIT2 ; GET_BIT1: SETB RAW_BIT ; set RAW_BIT for 1 bit state GET_BIT2: POP ACC ; restore entry R0 MOV R0, A RET ; exit with RAW_BIT as bit state ;-=-=-=-=-=-=-= ;NAME: PUT_BIT ; Used to put a bit into the raw bit buffer ; from the RAW_BIT bit. Entry R0 is the bit number ; that is preserved. ;-=-=-=-=-=-=-= PUT_BIT: MOV A, R0 PUSH ACC ; save entry bit number ; RR A ; make byte offset number RR A RR A ANL A, #01FH ; mask the byte number ADD A, #BIT_BUF ; make pointer to byte MOV R0, A ; save buffer offset into R0 POP ACC ; get copy of bit number PUSH ACC ANL A, #007H ; isolate 0-7 number CALL BIT_MSK ; convert bit # to a mask JB RAW_BIT, PUT_BIT1 ; save a "1" bit ; PUT_BIT0: CPL A ; make the NOT of the bit mask ANL A, @R0 ; clear bit in buffer byte JMP PUT_BIT2 ; PUT_BIT1: ORL A, @R0 ; set bit in buffer byte PUT_BIT2: MOV @R0, A ; store new bit value to buffer ; POP ACC MOV R0, A ; restore entry R0 RET ; exit with bit set ;-=-=-=-=-=-=-= ;NAME: BIT_MSK ; Used to convert a bit number to a byte mask ; Entry A is the 0-7 bit number ; Exit A is the bit mask ;-=-=-=-=-=-=-= BIT_MSK: INC A MOVC A, @A+PC RET ; DB 00000001B ; Bit 0 <- 0 DB 00000010B ; Bit 1 <- 1 DB 00000100B ; Bit 2 <- 2 DB 00001000B ; Bit 3 <- 3 DB 00010000B ; Bit 4 <- 4 DB 00100000B ; Bit 5 <- 5 DB 01000000B ; Bit 6 <- 6 DB 10000000B ; Bit 7 <- 7