PIC12 TRIS Register not setting - c

Question

I'm trying to program a PIC12C508A to do a simple LED learning circuit. I've read some examples, the Microchip Datasheet, pic12c508a.h and pic12c508a.inc. I've tried to set the TRIS register using a C program and an ASM program but it does not take. Using MPLAB X, the XC8 compiler, and the built in simulator to check the SFR registers I can see that the TRIS is not updating even when the WREG holds the correct values. If anyone has experience with this please check out my code and see if I am doing something wrong.
#include <xc.h>
// -- CONFIG
#pragma config MCLRE = ON // RA5/MCLR/VPP Pin Function Select bit (RA5/MCLR/VPP pin function is digital input, MCLR internally tied to VDD)
#pragma config WDT = OFF // Turn Watchdog Timer Off.
#pragma config CP = OFF // Flash Program Memory Code Protection bit (Code protection off)
#pragma config OSC = IntRC // Internal RC Oscillator
// -- Internal Frequency
#define _XTAL_FREQ 400000
int main()
{
TRIS = 0b111010; // 0x3A
//---0-0 Set GP0 and GP2 as outputs
GPIO = 0b000100; // 0x04
//---1-0 Set GP2 as HIGH and GP0 as LOW
for(int countdown = 10; countdown > 0; --countdown) {
__delay_ms(60000); // Delay 1 minute.
}
GPIO = 0b000001; // 0x01
//---0-1 Set GP2 as LOW and GP0 as HIGH
while(1)
NOP();
}
I also tried it an assembly which is pretty much identical to the Gooligum tutorials for baseline PIC models.
list p=12c508a
#include <p12c508a.inc>
__CONFIG _MCLRE_ON & _CP_OFF & _WDT_OFF & _IntRC_OSC
RCCAL CODE 0x0FF ; Processor Reset Vector
res 1 ; Hold internal RC cal value, as a movlw k
RESET CODE 0x000 ; RESET VECTOR
movwf OSCCAL ; Factory Calibration
start
movlw b'111010' ; Configure GP0/GP2 as outputs
tris GPIO ;
movlw b'000100' ; Set GP2 HIGH - GREEN LED
movwf GPIO
goto $ ; loop forever
END
This all seems pretty straight forward but when I use breakpoints and examine the SFR registers in the simulator I can see that the GPIO and TRIS registers never are changed even though the WREG will hold the correct values. I've examined the ASM output that the XC8 compiler generates and it is almost identical to the ASM I wrote when it comes to setting the registers.
I've also tried using HEX values and straight integer values and the results are the same.

Answer 1

The answer is that the crystal frequency defined at the top of the program was way beyond the real actual value
#define _XTAL_FREQ 400000 //that's 400KHz INTOSC, impossible
Instead it should be
#define _XTAL_FREQ 4000000 //That's 4MHz INTOSC
#Justin pointed it out in the comment below it's original post.

Answer 2

First, in order to use GP2 as an output, do you need to clear the T0CS in the OPTION register ?
Second, I observe this in the manual:
Note: A read of the ports reads the pins, not the output data latches.
That is, if an output driver on a pin is enabled and driven high, but
the external system is holding it low, a read of the port will
indicate that the pin is low.
but I guess the simulator will assume the external system is not holding down the pin.
Third, BCF and BSF instructions look like a better way of waggling GP2 and GP0 independent of whatever else is going on in the GPIO.
I'm sorry, but other than that I don't know what to suggest.

Answer 3

You can try different GPIO, because according to the documentation, GP2 may be controlled by the option register.