CODE_SEG	SEGMENT CODE 
DATA_SEG	SEGMENT DATA
STACK_SEG	SEGMENT	IDATA

SPK	BIT	P3.7

	RSEG	DATA_SEG
FRQ:   DS   1
TMP:   DS   1

	RSEG	STACK_SEG
STACK:	DS	20

;===============================================================================
CSEG	AT	00000H
	LJMP	MAIN


CSEG	AT	0000BH
	LJMP	TIMER0
	
	
	
;===============================================================================

	RSEG	CODE_SEG
MAIN:
	USING	0
	
	MOV	SP,#(STACK-1)
	
	MOV  	TMOD,#01H
	CLR  	A
	MOV  	FRQ,A
	MOV  	TH0,A
	MOV  	TL0,#0FFH
	SETB 	TR0
	MOV  	IE,#082H
	
MAIN_LP:

	INC  	FRQ
	
	MOV  	R7,#04		; 
	LCALL	DELAYMS

	SJMP 	MAIN_LP
	
; END OF main

;===============================================================================


TIMER0:
	MOV  	TH0,#0FEH
	MOV  	TL0,frq
	CPL  	SPK
	RETI 	
; END OF TIMER0


;===============================================================================
DELAYMS:
; 延時子程序
; 傳入參數：R7 --- 延時值(MS) 
; 返回值：無

	MOV	A,R7
	JZ	END_DLYMS	
DLY_LP1:
	MOV	R6,#185
DLY_LP2:
	NOP
	NOP
	NOP
	DJNZ	R6,DLY_LP2
	DJNZ	R7,DLY_LP1

END_DLYMS:
	RET 

	END