Hello List

I'm taking an existing circuit board from the 16C67 to the 16F877.
Everything seems to work normally except for a bit-banging routine which
manually controls an RS-232 driver (the USART is tied up elsewhere).  For
some reason, the 232 communication fails frequently on the 877 but not on
the 67.  To make matters more confusing, this problem only occurs with
burned chips, and does not occur on the MPLAB ICE.  The 232 handling is NOT
going through the USART -- it is being handled directly by code.

As far as I know, the only code differences that are necessary to move over
to the 877 are the following initialization commands:


  bsf  ADCON1, PCFG2 ; the F877 automaitically configures
  bsf  ADCON1, PCFG1 ; certain pins as AtoD.  This makes all the pins
digital.


  clrf PIR2   ; added for 877
  clrf ADCON0

page_2 ; added for 877
  clrf p2_EEDATA
  clrf p2_EEADR
  clrf p2_EEDATH
  clrf  p2_EEADRH

  page_3   ; added for 877
  clrf p3_EECON1   ; disables writes to onboard EEPROM
  clrf p3_EECON2

My initial suspicion was that some register was not being initialized
properly.  My thought is that the Emulator initializes unspecified registers
differently than the ProMate programmer and that this explains why the one
fails where the other succeeds.  However, I have examined every register and
bit which differs between the two units and I believe that I have addressed
whatever differences exist.

I have checked and triple-checked the ProMate settings.  Stepping through
code is of limited use since it works on the Emulator and not on the burned
chip.

Any ideas?

A million thanks,

Barnaby Thieme
Product Engineer, SP Controls, Inc.
bthieme@spcontrols.com

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