;gg202.asm/forsum2
;for 讀A口送B口<芯片8255A：A口接8開關(guān),B口接LED，pc7接1S脈沖>
;for 產(chǎn)生1S脈沖<芯片8253-5>
;2005-05
;lcy/p_Sa
data	SEGMENT
        PA	EQU	280h
        PB	EQU	281h
        PC	EQU	282h
        PCTL	EQU	283h
        
        T0	EQU	288H
        T1	EQU	289H
        T2	EQU	28aH
        TCTL	EQU   28bH 
data	ENDS
stack0 SEGMENT para stack
        DW	20h	DUP(0)
stack0 ENDS
        
coseg	SEGMENT
        ASSUME CS:coseg,DS:data,SS:stack0
start:  MOV AX, data
        MOV DS, AX
;================MOV-DS-AX==============  
        MOV DX, TCTL
        MOV AL, 27h	;00-10-011-1B:0通道，高8位，方式3（方波發(fā)生器），BCD記數(shù)
        OUT DX, AL
        MOV DX, T0
        MOV AL, 10h	;1us=>1ms方波
        OUT DX, AL
        MOV DX, TCTL
        MOV AL, 65h	;01-10-010-1B:1通道，高8位，方式2（頻率發(fā)生器），BCD記數(shù)
        OUT DX, AL
        MOV DX, T1
        MOV AL, 10h	;1ms=>1s脈沖
        OUT DX, AL
                
        MOV AL, 98h	;1-0011-000B:A口方式0輸入，B口方式0輸出
        MOV DX, PCTL
        OUT DX, AL
        MOV CX, 10h
     L1:MOV DX, PC
        IN  AL, DX
        TEST AL, 80h
        JZ  L1		;判斷pc7上升沿
        MOV DX, PA
        IN  AL, DX
        MOV	DX, PB
        OUT DX, AL
        MOV DX, PC
     L2:IN  AL, DX
        TEST AL, 80h
        JNZ  L2		;判斷pc7下降沿
        LOOP L1
;================INT-21H================
        MOV AH, 4ch
        INT 21h
coseg	ENDS
        END	start