keypad.sdi

keyboard Realizing the keyboard control digital tube

,,,;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
,,,;
,,,;       KEYPAD.ASM      MPB     Ver 1.0         28-8-05
,,,;
,,,;       Reads keypad and shows digit on display
,,,;       Design file KEYPAD.DSN
,,,;
,,,;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
,,,
,,,        PROCESSOR 16F877
,,,
,,,PCL     EQU     002             ; Program Counter
,,,PORTC   EQU     007             ; 7-Segment display
,,,PORTD   EQU     008             ; 3x4 keypad
,,,
,,,TRISC   EQU     087             ; Data direction
,,,TRISD   EQU     088             ; registers
,,,
,,,Key     EQU     020             ; Count of keys
,,,
,,,; Initialise ports.........................................
,,,
00000000,1683 1303,,        BANKSEL TRISC           ; Display
00000002,0103,,        CLRW                    ; all outputs
00000003,0087,,        MOVWF   TRISC           ;
00000004,3007,,        MOVLW   B'00000111'     ; Keypad
00000005,0088,,        MOVWF   TRISD           ; bidirectional
,,,
00000006,1283 1303,,        BANKSEL PORTC           ; Display off
00000008,0187,,        CLRF    PORTC           ; initially
00000009,2830,,        GOTO    main            ; jump to main
,,,
,,,; Check a row of keys .....................................
,,,
0000000A,0AA0,row,row     INCF    Key             ; Count first key
0000000B,1C08,,        BTFSS   PORTD,0         ; Check key
0000000C,281D,,        GOTO    found           ; and quit if on
,,,
0000000D,0AA0,,        INCF    Key             ; and repeat
0000000E,1C88,,        BTFSS   PORTD,1         ; for second
0000000F,281D,,        GOTO    found           ; key
,,,
00000010,0AA0,,        INCF    Key             ; and repeat
00000011,1D08,,        BTFSS   PORTD,2         ; for third
00000012,281D,,        GOTO    found           ; key
00000013,2818,,        GOTO    next            ; go for next row
,,,
,,,; Scan the keypad..........................................
,,,
00000014,01A0,scan,scan    CLRF    Key             ; Zero key count
00000015,1403,,        BSF     3,0             ; Set Carry Flag
00000016,1208,,        BCF     PORTD,4         ; Select first row
00000017,280A,newrow,newrow  GOTO    row             ; check row
,,,
00000018,1588,next,next    BSF     PORTD,3         ; Set fill bit
00000019,0D88,,        RLF     PORTD           ; Select next row
0000001A,1803,,        BTFSC   3,0             ; 0 into carry flag?
0000001B,2817,,        GOTO    newrow          ; if not, next row
0000001C,2814,,        GOTO    scan            ; if so, start again
,,,
0000001D,0008,found,found   RETURN                  ; quit with key count
,,,
,,,; Display code table.......................................
,,,
0000001E,0820,table,table   MOVF    Key,W           ; Get key count
0000001F,0782,,        ADDWF   PCL             ; and calculate jump
00000020,0000,,        NOP                     ; into table
00000021,340C,,        RETLW   B'00001100'     ; Code for '1'
00000022,34B6,,        RETLW   B'10110110'     ; Code for '2'
00000023,349E,,        RETLW   B'10011110'     ; Code for '3'
00000024,34CC,,        RETLW   B'11001100'     ; Code for '4'
00000025,34DA,,        RETLW   B'11011010'     ; Code for '5'
00000026,34F8,,        RETLW   B'11111000'     ; Code for '6'
00000027,340E,,        RETLW   B'00001110'     ; Code for '7'
00000028,34FE,,        RETLW   B'11111110'     ; Code for '8'
00000029,34CE,,        RETLW   B'11001110'     ; Code for '9'
0000002A,3492,,        RETLW   B'10010010'     ; Code for '*'
0000002B,347E,,        RETLW   B'01111110'     ; Code for '0'
0000002C,34EC,,        RETLW   B'11101100'     ; Code for '#'
,,,
,,,; Output display code......................................
,,,
0000002D,201E,show,show    CALL    table           ; Get display code
0000002E,0087,,        MOVWF   PORTC           ; and show it
0000002F,0008,,        RETURN
,,,
,,,;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
,,,
,,,; Read keypad & display....
,,,
00000030,30FF,main,main    MOVLW   0FF             ; Set all outputs
00000031,0088,,        MOVWF   PORTD           ; to keypad high
00000032,2014,,        CALL    scan            ; Get key number
00000033,202D,,        CALL    show            ; and dsiplay it
00000034,2830,,        GOTO    main            ; and repeat
,,,        END