input_timeout.asm

ASM code for sine inverter

;Timeout Waiting For Input Data, using Timer 0 with simple polling
;http://www.pjrc.com/tech/8051/board4/timers.html

;This examples demonstrates how to use Timer 0 to implement a
;simple timeout while waiting for input data.  This simple example
;waits for the user to type 10 characters.  The timeout for the 
;first character is 5 seconds, and then 1 second for each character
;thereafter.  If the user does not respond within this time, a
;timeout message is printed.



.equ    cout, 0x0030            ;Send Acc to serial port
.equ    cin, 0x0032             ;Get Acc from serial port
.equ    phex, 0x0034            ;Print Hex value of Acc
.equ    pstr, 0x0038            ;Print string pointed to by DPTR,
.equ    esc, 0x003E             ;Check for ESC key
.equ    newline, 0x0048         ;print CR/LF (13 and 10)


	.org	0x2000

begin:
	mov	r0, #0		;r0 counts number of bytes received
	clr	tr0		;make sure timer 0 is stopped
	clr	tf0		;clear the overflow flag
	anl	tmod, #0xF0	
	orl	tmod, #0x01	;set to mode 1 (without touching timer 1)
	mov	tl0, #0
	mov	th0, #0		;clear the timer 0 value
	mov	r2, #140	;140 overflows is 5 seconds
	mov	dptr, #msg_begin
	lcall	pstr
	setb	tr0		;start the timing
waiting_loop:
	jb	ri, get_input	;did we receive another byte ??
	jnb	tf0, waiting_loop ;did timer 0 overflow?
	clr	tf0
	 ;mov	a, r2		;uncomment to "see" the countdown
	 ;lcall	phex
	djnz	r2, waiting_loop
timeout:
	mov	dptr, #msg_timeout
	lcall	pstr
	sjmp	ending
get_input:
	lcall	cin		;get the user input
	lcall	cout		;echo it back to their screen
	mov	r2, #28		;reset timeout to 1 second
	inc	r0
	cjne	r0, #10, waiting_loop
got_all_input:
	mov	dptr, #msg_ok
	lcall	pstr
ending:
	mov	dptr, #msg_end
	lcall	pstr
	lcall	cin
	ljmp	0


msg_begin:
	.db	13,10,13,10
	.db	"        Timeout Waiting For Input Data",13,10,13,10
	.db	"Please type 10 characters, before it's too late.....",13,10,0
msg_timeout:
	.db	13,10,13,10,"Timeout: Waited too long.",0
msg_ok:
	.db	13,10,13,10,"Ok: All 10 characters received within the allowed time.",0
msg_end:
	.db	13,10,13,10,"Press a key to reboot",0