Hi Doug,

It is a Homer moment - for me.

I *think* that this application is the only one that does not go directly to
the PIC16F877.  The problem is that I didn't make sure that this code (it's
only a few lines, so why bother right?) changed the PORTA bits to Digital
I/O when the PIC16F877 is selected.

Here is the corrected code:

 title  "ledon - Turn on a LED when a Button is Pressed"
;
;  This is the First Program to be Burned in and Run in a PIC.
;
;  The Program simply sets up Bit 0 of Port "A" to Output and then
;   Sets it Low when RA0 is pulled low.
;
;  Hardware Notes:
;   _MCLR is tied through a 4.7K Resistor to Vcc and PWRT is Enabled
;   A 220 Ohm Resistor and LED is attached to PORTB.0 and Vcc
;   A 10K pull up is connected to RA0 and it's state is passed to
;    RB0
;
;  Myke Predko
;  99.12.03
;  02.01.10 - Added Write to "ADCON1" to Put PORTA in Digial I/O
;              mode
;
  LIST R=DEC
 ifdef __16F84
  INCLUDE "p16f84.inc"
 endif
 ifdef __16F877
  INCLUDE "p16f877.inc"
 endif

;  Registers

 ifdef __16F84
 __CONFIG _CP_OFF & _WDT_OFF & _XT_OSC & _PWRTE_ON
 else
 __CONFIG _CP_OFF & _DEBUG_OFF & _XT_OSC & _PWRTE_ON  & _WDT_OFF & _LVP_OFF
& _WRT_ENABLE_ON & _BODEN_ON & _CPD_OFF
 endif

 __IDLOCS 0x01234

  PAGE
;  Mainline of ledon

 org     0

  nop    ;  "nop" is Required for Emulators

  bsf    PORTB, 0               ;  Make the LED on PORTB.0 "off"

  bsf    STATUS, RP0            ;  Goto Bank 1 to set Port Direction
  bcf    TRISB ^ 0x080, 0       ;  Set RB0 to Output
 ifdef __16F877
  movlw  7   ;  Make PortA Digital I/O for PIC16F877
  movwf  ADCON1 ^ 0x080
 else
  nop    ;  Make sure Space required is always the same
  nop
 endif
  bcf    STATUS, RP0            ;  Go back to Bank 0

Loop
  movf   PORTA, w  ;  Simply Transfer PORTA.0 to PORTB.0
  movwf  PORTB

  goto   Loop


 end


I put the code to write to ADCON1 as conditionally assembling so that there
wouldn't be an problem with the PIC16F84.

Sorry for the hassles:

D'Oh!

myke

----- Original Message -----
From: "Doug Hemingway" <DougHemi@MAC.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, February 05, 2002 1:28 AM
Subject: [PIC]: 16F877 Oscillator


> Sorry, I didn't put the correct subject router the first time.
>
> I have just gotten my first 16F877 and have programmed it to do a simple
> "turn on the led" program  (the LEDON program in Myke's book, where RB0
> should follow the state of RA0).  It is so simple it doesn't work.  The XT
> oscillator config is programmed, but on the OSC1/CLKIN pin 13 I see a
> tristate condition.  On OSC2/CLKOUT pin 14 I see the oscillator frequency.
> I am using a 3 pin ceramic resonator with the center pin grounded. Both
Vdd
> and both Vss pins are correctly connected, and the MPU is bypassed with
> .1uF.  MCLR is tied high through a 1K resistor.  Anyone have any
suggestions
> on how to get past this Homer Moment (D-OH!)
>
> TIA,
> Doug Hemingway
>
> --
> http://www.piclist.com hint: To leave the PICList
> mailto:piclist-unsubscribe-request@mitvma.mit.edu
>
>
>

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