hi daire,

sorry i confused u with my assemble program!
plz find below the program which worked properly for me with the comments!
made some more modifications in ISS to suit exactly ur requirement!

I am clearing the internal RAM first so i am using R0 as a pointer the i am writing #00H to all RAM locations!

I am initialising only timer0 only!


there r 3 steps involved,
1)kicking ON ur transmitter that is generating the square wave.
2)every time ur square wave toggles u r going to increment a 16bit counter which at last is going to give u how may square pulse has gone out!
3) when u receive ur signal then u have to stop the timer,so that u r stopping the generation of square wave!At this time if u read ur 16bit counter it will give u the square pulse went out!

;program with comments
START1:
.ORG 0000H
LJMP 0050H ;start code execution from here
INT1:
.ORG 0013H
RETI ;INTERRUPT SERVICE SUBROUTINE...
TIM_INT0:
.ORG 000BH
LJMP 1000H ;TIMER Interrupt zero
TIM_INT1:
.ORG 001BH
RETI ;TIMER Interrupt one (this is given since if a timer1 interrupt occurs without any actual tiggering then it should not cause the uC to run wild same for timer2 also; this is not timer initialisation)
TIM_INT2:
.ORG 002BH
RETI ;TIMER Interrupt TWO
CODE_BEGIN:
.ORG 0050H

INITIAL: MOV IE,#00H ;Disable interruptS

;the following code CLEARs INTERNAL RAM
;################################################
MOV R0,#FFH ;CLEAR INTERNAL RAM
MOV A,#00H ;
CLEAR_RAM: MOV @R0,A ;
DJNZ R0,CLEAR_RAM ;
;#################################################
;TIMER0 INITIALISATION
;@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
CLR TR0 ;stop timer0
CLR TF0 ;clear timer0
;(the frequency u want to generate (ie., 40Khz) depends on the value in value1 and value2 u select here. u have to calculate what value should be load if u want to generate 40Khz and divide it by 2 and load it here )
MOV TH0,#VALUE1
MOV TL0,#VALUE2
MOV TMOD,#11H ;TIMER0 MODE 1
SETB P1.0 ; LET ME ASSUME U R USING P1.0 FOR ;GENERATING SQUARE WAVE

MOV IE,#82H
SETB TR0 ;StART TIMER0
;@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
;count1 and count2 r the internal reg. which r going to contain how may square pulse u have transmitted.u have to declare this reg's

MOV COUNT1,#00H ;
MOV COUNT2,#00H

;(YOUR ANALOG INPUT will be CHECKed HERE continously in the main program ,I AM JUST ASSUMING IT TO BE BIT ADDRESSABLE)

MAIN:
CLR C
MOV C,PORT_PIN ;USED APPROPRIATE LOGIC TO CHECK UR ANALOG PIN
JC RXED ;( when i receive the signal in the analog input we will jump to RXED routine)

JMP MAIN
RXED:
;HOW MANY TIMES UR COUNTER HAS RUN or how may suare pulse u have transmitted WILL BE STORED IN COUNT1 AND COUNT2 REGs)

CLR TR0
CLR TF0
JMP UR_ROUTINE
UR_ROUTINE:

;Here if u read the count1 and count2 values it will give u the no. of square pulse send out. so that is the data u want to manipulate to determind the exact distance.

;TIMER0
;This is the ISS for timer0 when
.ORG 1000H
CLR TR0 ;stopping timer0
CLR TF0 ;clearing timer0
CPL P1.0 ; TOGGLEING TO GET SQUARE WAVE
clr c
mov c,p1.0
jc out1 ;(checking for one pulse if yes then increment the 16 bit counter)
mov a,count1
add a,#01h
mov count1,a
JNC OUT1
CLR C
INC COUNT2 ;16 BIT COUNTING IS USED U SHALL MODIFY AS U REQUIRE
OUT1:
MOV TH0,VALUE1
MOV TL0,VALUE2
SETB TR0
RETI

daire plz cut and paste the program in notepad then go through it!

i Want some more clarification daire,

1)Have u sucessfully generated the 40Khz square pulse using timer???
2)I have implemented the project through a USD kit so i don't have to bother about the rxed signal!
i will get a pulse when i rx the reflected signal so i will stop my counter then!
now in ur case what is mean by this analog input?? Is it an ADC input ???
since i worked only with 80c52 i dont have idea about ADuC812 any way i am trying to get its datasheets!
3) this distance measurement is a part of ur project or this itself u have taken as a project??

keep me informed about ur progress and troubles if u face any!

u shall mail me to

danaraja_b@btlpkd.com


All the best!
rgds,
dana