🚀 go-pugleaf

Hello everybody!

Got another programming problem with my 8051.

I am trying to get an LED to blink every second for 1 second using
Timer 0.  The program is supposed to Interupt driven.

I have been able to write the program using a polling method..  I just
am having trouble getting the Interupt driven program to work.

I want the LED to change state once every second..  So, for my 8 Mhtz
8051, that would mean that about one second would elapse after
Timer 0 has overflowed the FULL 16 bits 11 times.

So,  I have Timer 0 interupt enabled and wrote the interupt handler.

The handler checks to see how many times the Interupt has been called.  The
value is stored in R3.  Each time the interupt is called, R3 is incremented.
If R3 = 11, then one second has passed, time to change the state of the
LED.  If R3 <> 11, just reti.

THis is not working....  The LED blinks randomly for about 2 seconds, then
turns off and stays off...  

Anybody have any ideas about what is going on here?



=====
seg data at 0
REGISTERS: rb 8
 
seg code 
anl 0x087, #11111011b         ;;; Turn off watchdog timer.

STROBE      equ  P0.0


clr TR1             ;;;  Stop Timer1

mov TMOD, #00000001b ;;;  Timer 0 in 16 bit mode
 
setb EA
setb ET0             ;;;  Timer0 Interupt Enabled

mov TH0, #0d         ;;;  Set High Byte of Timer Val
mov TL0, #0d         ;;;  Set Low Byte of Timer Val
		     ;;;  Sets the Timer for full Time.
                     ;;;  ie.   256 - 256 = 0

mov R3, #0d          ;;;  TimerInts = 0
setb STROBE          ;;;  LED is off

setb TR0             ;;;  Start Timer0
sjmp $               ;;;  Loop until Interupt...

org 0x0B             ;;; Timer Interupt service routine.
Service_Timer:
   inc R3   
   cjne R3,#11d,Cont   
   cpl STROBE
   mov R3, #0d
   reti
   Cont:  reti 

-- 
pegasus@csd4.csd.uwm.edu                David R. Hucke
                                        UW-Milwaukee Film Major
--