;mm401_2.asm
;for 鋸齒波16次<8086>
;2005-05
;p_Sa/lcy
data	SEGMENT
        PA	EQU	280h
        PB	EQU	281h
        PC	EQU	282h
        PCTL	EQU	283h	;Y0(280h-287h)
        
        T0	EQU	288H
        T1	EQU	289H
        T2	EQU	28aH
        TCTL	EQU   28bH	;Y1(288h-28bh)
        
        PORT	EQU	290H	;Y2(290h-297h)
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==============
      ;;8253和8255的初始化：
        MOV DX, TCTL
        MOV AL, 25h	;00-10-010-1B:0通道，高8位，方式（頻率發(fā)生器），BCD記數(shù)
        OUT DX, AL
        MOV DX, T0
        MOV AL, 10h	;1us=>1ms頻率
        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

      ;;總的波形次數(shù)ffffh次：
        MOV SI, 0
     l0:MOV CX, 16
        ;MOV CX, 32
        MOV BL,7fh	;從2.5V開(kāi)始
     L1:MOV DX, PC
     p1:IN  AL, DX	;p1循環(huán)判斷pc7的脈沖是否到來(lái)
        TEST AL, 80h
        JE  p1
      
        MOV DX, PORT
        MOV AL, BL
        OUT DX, AL
        ADD BL, 08H	;16次循環(huán)16×08h=80h，80h+7fh=ffh，達(dá)到5V
        
        MOV DX, PC
     p2:IN  AL, DX	;p2循環(huán)判斷pc7的脈沖是否已經(jīng)過(guò)去
        TEST AL, 80h
        JNE  p2        
        LOOP l1
        DEC SI
        JNE l0        
         
;================INT-21H================
        MOV AH, 4ch
        INT 21h
coseg	ENDS
        END	start