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Guest
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| Trouble with the PIC16F873A at 3.3V |
 Posted: Thu Jan 22, 2009 8:59 am |
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Hi All,
I can't get a new prototype to work with the 16F873A at 3.3V. The circuit is correct because it was extensively debugged with a 16F73 device running at 5V. I ultimately need to run this circuit at 3.3V to be compatible with an XBee Pro radio modem. I was orginally planning to use the 16F73 until I realized (belatedly) that it does not work with the ICD-U40, and that is why I switched to the new PIC. Anyway, I ran the board at 5V with the 16F73 (without the Xbee Pro) to do the initial code development until the 16F873A chips arrived. This morning I changed the PIC to the 16F873A, and the regulator to a 78M33 (3.3V), and recompiled my code for the 16F873A. I can program the chip just fine with the ICD-U40, but the previously tested code does not run at all. Here is a simple test program that blinks the power LED, and this program does not run.
| Code: |
//-----< Include Files, setup fuses >-----
#include <16f873a.h>
#fuses XT, NOWDT, NOPROTECT, NOLVP
//-----< Compiler use statements >-----
// Tell compiler clock speed is 4.00 MHZ Crystal
#use delay(clock=4000000)
//-----< General Program Defines >-----
#define Pwr_Led Pin_A1 // Green Power LED
void main(void)
{
int8 iIndex;
output_low(Pwr_LED);
// Here we blip the Power LED at power-up to show that the interface is working
for ( iIndex = 0 ; iIndex < 3 ; iIndex++ )
{
output_high(PWR_LED);
delay_ms(250);
output_low(PWR_LED);
delay_ms(250);
}
// Here we leave the Power LED ON
output_high(PWR_LED);
} // end Main
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My compiler is v4.050. I checked for any differences (fuses, etc.) between the 16F73 and the 16F873A and didn't see anything that would seem to explain this problem. I'm beginning to wonder if this version of the compiler was robust for the 16f873A?
Thanks,
Tim |
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PICoHolic
Joined: 04 Jan 2005
Posts: 224
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| Posted: Thu Jan 22, 2009 9:12 am |
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| Try using 16LF873A instead of 16F873A |
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Guest
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| Posted: Thu Jan 22, 2009 5:48 pm |
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Hi All,
Well, I solved the problem! The issue is that the 16F873A requires the NOBROWNOUT fuse for operation below 4V. I found this tidbit after a thorough read of the datasheet. I didn't think of this initially because this was the first time I've ever operated at a supply voltage less than 5V!
Tim |
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