ADC0804 with ATt89s52 PROBLEM IN GETTNG VALUU

[kirtan.gopal]

I have implement in Proteus8 its working but not on physical model it always give 254 value in return.help me ......

ADC:  
  MOV P1,#00H   
  CLR P2.6  
  SETB P2.5  
  CLR P2.4 
  ACALL  DELAY_200M
  ACALL  DELAY_200M
  SETB P2.4 ; low to high pulse to WR for starting conversion
    MOV R7,#225
Del_1_Sec4:
  DJNZ  R7,Del_1_Sec4
  WAIT: JB P2.7,WAIT ; polls until INTR=0
    CLR P2.6 ; ensures CS=0
  MOV R7,#225
Del_1_Sec0:
  DJNZ  R7,Del_1_Sec0
  CLR P2.5 ; high to low pulse to RD for reading the data from ADC
  MOV R7,#225
Del_1_Sec1:
  DJNZ  R7,Del_1_Sec1
  MOV VALUE,P0
   SETB P2.6
  SETB P2.5
  RET

where
wr- p2.4
rd-p2.5
cs p2.6
intr 2.7

 

[milan.rajik]

Zip and post your exact hardware circuit as Proteus file or as .png image.