TITLE "Key Stroke Wake Up"
LIST P = 16C54
;******************************************************
; Program demonstrating key stroke wake up for
; the PIC16CXX. Program has been implemented for
; two keys, but can be extended for more keys.
; When SW1 is pressed a green LED lights up.
; When SW2 is pressed a red LED lights up.
;******************************************************
;
; Define equates
;
PC EQU 2
PORT_B EQU 6
SCAN1 EQU 2
SCAN2 EQU 3
SW1 EQU 0
SW2 EQU 1
GRN_LED EQU 4
RED_LED EQU 5
MSEC_20 EQU D'20'
DB1 EQU 8
GP EQU 8
DB2 EQU 9
;
;PORT_B ASSIGNMENTS:
; 0 --> SW1 INPUT
; 1 --> SW2 INPUT
; 2 --> SCAN1 OUTPUT
; 3 --> SCAN2 OUTPUT
; 4 --> GRN_LED OUTPUT
; 5 --> RED_LED OUTPUT
; 6&7 --> ASSIGNED AS DUMMY OUTPUTS
PAGE
;
;
ORG 0
;
START
CALL INIT_PORT_B ;INITIALIZE PORT B
CALL DELAY ;DELAY 20 MSECS
CALL SCAN_KEYS ;GET KEY VALUES
MOVWF GP ;SAVE IN RAM
BTFSC GP,SW1 ;SKIP IF SW1 NOT PRESSED
CALL TURN_GREEN_ON ;ELSE DO ROUTINE
BTFSC GP,SW2 ;SKIP IF SW2 NOT PRESSED
CALL TURN_RED_ON ;ELSE DO ROUTINE
CHK_FOR_KEY
CALL DELAY ;DELAY FOR 20 MSEC
CALL SCAN_KEYS ;GET KEY HIT
XORLW 0 ;EXCL. OR WITH 0
BNZ CHK_FOR_KEY ;KEY STILL PRESSED
;THEN LOOP
NO_KEY_PRESSED
BCF PORT_B,SCAN1 ;SET SCAN LINES LOW
BCF PORT_B,SCAN2 ; /
SLEEP ;SLEEP
;
PAGE
;
INIT_PORT_B
MOVLW B'00000011' ; config RB0, 1 as i/p's
TRIS PORT_B ; and RB2-7 as o/p's
MOVLW 0FFh
MOVWF PORT_B ;DEFAULT VALUES FOR PORT_B
RETLW 0 ;RETURN WITH NO ERROR
;
;This routine, scans two keys and returns the following:
; 0 if no key is pressed
; 1 if SW1 is pressd
; 2 if SW2 is pressed
; 3 if SW1 and SW2 are pressed
;
SCAN_KEYS
BCF PORT_B,SCAN1 ;ENABLE SCAN FOR SW1
BCF PORT_B,SCAN2 ;EANBLE SCAN FOR SW2
MOVLW B'00000011' ;LOAD MASK IN W
ANDWF PORT_B,0 ;AND WITH PORT
BSF PORT_B,SCAN1 ;DISABLE SCAN
BSF PORT_B,SCAN2 ; /
ADDWF PC,1 ;GET OFFSET TO TABLE
RETLW 3 ;SW1 AND SW2 PRESSED
RETLW 2 ;SW2 PRESSED
RETLW 1 ;SW1 PRESSED
RETLW 0 ;NO KEY PRESSED
;
;DELAY, IS A APPROX. WAIT FOR 20.4mSECS, FOR A SYSTEM
;USING A 2 Mhz CRYSTAL CLOCK.
DELAY
MOVLW MSEC_20
MOVWF DB1
DLY1
CLRF DB2
DECFSZ DB1
GOTO DLY2
RETLW 0
DLY2
DECFSZ DB2 ;INNER LOOP = 1.02 MSEC.
GOTO DLY2 ; /
GOTO DLY1
;
;
TURN_GREEN_ON
BCF PORT_B,GRN_LED
RETLW 0
;
TURN_RED_ON
BCF PORT_B,RED_LED
RETLW 0
;
END |
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66821730(技术支持)
