;T0832-2.asm
;D/A轉換實驗，產生三角波

;****************根據查看端口資源修改下列符號值*******************
IOY0         EQU   9C00H         ;片選IOY0對應的端口始地址
;*****************************************************************
DA0832       EQU   IOY0+00H*4    ;DA0832的端口地址

STACK1 SEGMENT STACK
        DW 256 DUP(?)
STACK1 ENDS

DATA SEGMENT
STR1   DB  'DA0832: Triangle Wave $'        ;定義顯示的字符串
DATA ENDS

CODE SEGMENT
	ASSUME CS:CODE,DS:DATA

START:  MOV AX,DATA
        MOV DS,AX
        
        MOV DX,OFFSET STR1        ;顯示字符串  
        MOV AH,9
        INT 21H

LOOP1:  MOV AL,00H                ;D/A轉換起始值
UP:     MOV DX,DA0832             ;啟動D/A轉換
        OUT DX,AL
        CALL DALLY

	    INC AL                    
	    CMP AL,7FH
        JNE UP

DOWN:   MOV DX,DA0832
        OUT DX,AL
        CALL DALLY

        DEC AL
        CMP AL,00H
        JNE DOWN

        MOV AH,1                  ;判斷是否有按鍵按下
        INT 16H
        JZ  LOOP1                 ;無按鍵則跳回繼續循環，有則退出

QUIT:   MOV AX,4C00H              ;結束程序退出
        INT 21H

DALLY PROC NEAR	                  ;軟件延時子程序
        PUSH CX
	    PUSH AX
        MOV CX,0010H
D1:     MOV AX,0100H
D2:	    DEC AX
	    JNZ D2
	    LOOP D1
	    POP AX
	    POP CX
	  RET
DALLY ENDP

CODE ENDS
     END START