功能说明：
利用定时器1的定时模式制作一个秒表。
电路说明：
HT48R50A-1 的端口A，端口C控制4个共阳极七段显示器以显示秒表的s及1/100s。
HT48R50A-1 的复位键SW1作为秒表的开始计时，停止计时和回零按键。
程序：
; ***************************************************
; * Filename : 9712a.ASM *
; * Function : Stop watch *
; * Microprocessor : HT48R50A-1/28SKDIP-A *
; * Crystal : 4MHz *
; ***************************************************
#INCLUDE HT48R50A-1.INC
TIMER_START EQU 55H
TIMER_STOP EQU 66H
;----------------------------------------------------
DATA .SECTION AT 60H 'DATA'
WARM_RESET DB ? ;[60H]
DELAY_COUNTER DB ? ;[61H]
DISPLAY_DATA DB ? ;[62H]
DISPLAY_COUNTER DB ? ;[63H]
DISPLAY_SHIFT DB ? ;[64H]
SECOND DB 4 DUP(?);[65H]
;----------------------------------------------------
CODE .SECTION AT 00H 'CODE'
ORG 00H
JMP START
ORG 0CH
JMP TIMER1
ORG 20H
START:
CLR PAC
CLR PCC
MOV A,WARM_RESET
SUB A,TIMER_START
SZ ACC
JMP TIMER_STOP_C
MOV A,TIMER_STOP
MOV WARM_RESET,A
JMP TIMER_START_GO
TIMER_STOP_C:
MOV A,WARM_RESET
SUB A,TIMER_STOP
SZ ACC
JMP TIMER_ONE
CLR WARM_RESET
JMP DISPLAY
TIMER_ONE:
MOV A,TIMER_START
MOV WARM_RESET,A
CALL CLEAN
JMP DISPLAY
TIMER_START_GO:
MOV A,09H
MOV INTC,A
MOV A,80H
MOV TMR1C,A
MOV A,0F0H
MOV TMR1L,A
MOV A,0D8H
MOV TMR1H,A
SET TMR1C.4
CALL CLEAN
TIMER:
MOV A,OFFSET SECOND
MOV MP1,A
MOV A,R1
SUB A,0AH
SZ ACC
JMP DISPLAY
CLR R1
INC MP1
INC R1
MOV A,R1
SUB A,0AH
SZ ACC
JMP DISPLAY
CLR R1
INC MP1
INC R1
MOV A,R1
SUB A,0AH
SZ ACC
JMP DISPLAY
CLR R1
INC MP1
INC R1
MOV A,R1
SUB A,06H
SZ ACC
JMP DISPLAY
CALL CLEAN
DISPLAY:
MOV A,OFFSET SECOND
MOV MP0,A
MOV A,0FEH
MOV DISPLAY_SHIFT,A
MOV A,04H
MOV DISPLAY_COUNTER,A
DISPLAY_LOOP:
MOV A,R0
MOV TBLP,A
TABRDL DISPLAY_DATA
MOV A,DISPLAY_DATA
MOV PA,A
MOV A,DISPLAY_SHIFT
MOV PC,A
INC MP0
RL DISPLAY_SHIFT
CALL DELAY
SDZ DISPLAY_COUNTER
JMP DISPLAY_LOOP
MOV A,WARM_RESET
SUB A,TIMER_STOP
SZ ACC
JMP DISPLAY
JMP TIMER
RET
;----------------------------------------------------
TIMER1:
INC SECOND
RETI
;----------------------------------------------------
CLEAN PROC
MOV A,OFFSET SECOND
MOV MP1,A
MOV A,04H
MOV DISPLAY_COUNTER,A
CLEAN_LOOP:
CLR R1
INC MP1
SDZ DISPLAY_COUNTER
JMP CLEAN_LOOP
RET
CLEAN ENDP
;----------------------------------------------------
DELAY PROC
MOV A,0FFH
MOV DELAY_COUNTER,A
WAIT:
SDZ DELAY_COUNTER
JMP WAIT
RET
DELAY ENDP
;----------------------------------------------------
ORG 0F00H
DC 081H,0CFH,092H,086H ;0123
DC 0CCH,0A4H,0A0H,08FH ;4567
DC 080H,084H ;89
;----------------------------------------------------
END