t0_m0_c_gs.a51

C51 Timer 0 的使用 Timer_0_mode_0_counter_gate_soft

$INCLUDE   (reg_c51.INC)

org 000h
ljmp begin

org 00Bh
ljmp it_timer0

;/**
; * FUNCTION_PURPOSE: This file set up timer 0 in mode 0 (13 bits counter) 
; * with a software gate. The counter count up at eatch negative transition.
; * The 13-bits register consist of all 8 bits of TH0 and the lower 5 bits   
; * of TL0. The upper 3 bits of TL0 are undeterminate and are ignored.   
; * FUNCTION_INPUTS: P3.4(T0) must be controlled by an external clock
; * FUNCTION_OUTPUTS: void
; */
org 0100h

begin:
	ANL TMOD,#0F0h;					/* Timer 0 mode 0 counter with software gate */
	ORL TMOD,#04h;			   	   /* GATE0=0; C/T0#=1; M10=0; M00=0; */
	
	MOV TH0,#00h;			         /* init values */
	MOV TL0,#00h;		
	SETB ET0;						   /* enable timer0 interrupt */
	SETB EA;                      /* enable interrupts */
	SETB TR0;						   /* timer0 run */
	JMP $;						      /* endless  */
  


;/**
; * FUNCTION_PURPOSE: timer0 interrupt
; * FUNCTION_INPUTS: void
; * FUNCTION_OUTPUTS: P1.0 toggle period = 2 * 8192 * P3.4(T0) period 
; */
it_timer0:

	CLR TF0;						/* reset  interrupt flag (already done by hardware)*/
	CPL P1.0;					/* P1.0 toggle when interrupt. */
   RETI

end