I am able to get an a2d value from my 877 chip reding value from a
potentiometer connected to chip (using chips vdd as vref). after i put the
value's from ADRESH into a user register (via W of course) i perform an
ADDWF where W=D'55' to see whether or not the A2d value is greater than 200
or not (this is my threshold level i am interested in). the strange thing is
that the STATUS carry bit (bit 0) does not stay at 1 like it should when the
user register is 201 and greater. using leds, i am able to verify that the
status bit will only show a MSB carry when the user register is of the
following values:
201 through 207
217 through 231
247 through 255

in the other values the carry bit is 0 as verifed by leds. the pattern seems
to be that the status bit will only show a carry when the lower byte of the
user register being added to W is between 9 and 15, which coincides with a
lower byte carry (STAUS bit 1 D being set).

any thoughts? it is very perplexing.

some of the code:
Main
  call ad_portc
  goto Main

ad_portc
bsf ADCON0,GO ;Start A/D conversion
Wait
  btfsc ADCON0,GO ;  Wait for conversion to complete
  goto Wait

  movf  ADRESH,W       ;Write A/D result to PORTC
  movwf  PORTC ;LEDs
  movwf  Throttle
 movlw D'55'
  addwf  Throttle,W
   btfss   status, 0
FALSE   goto   false_10
TRUE     bsf     PORTB,0
GOTO    continue_10
false_10    bcf   PORTB,0
continue_10
return


thanks,

jeff

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.




--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.