M16 - PortC Non functional

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Matt_edwards

Level: Wannabe

Joined: Sat. Dec 14, 2002

Posts: 96 View posts

Location: Baulkham Hills, Australia

Posted by Matt_edwards: Fri. Oct 3, 2008 - 11:33 AM

I have the weirdest fault i have ever seen.
I have a new PCB that has some BCD switches connected to PORTC. I have 8 LEDs on PORTA and I am writing some simple code to check the hardware.

#include 
#include 
int main (void)
{
	// port 'A'
	DDRA = 0xff;	
	PORTA = 0x00;	 

	// port 'B'
	DDRB = 0xff;	
	PORTB = 0x00;	

	// port 'C'
	DDRC = 0x00;	
	PORTC = 0xff;	

	// port 'D'
	DDRD = 0x00;	
	PORTD = 0xff;	

	while(1) PORTA = PINC;
}

In this case PA2, PA3 PA4 & PA5 are always OFF ( LO)
IE PA0, PA1 PA6 and PA7 work as expected.

I have done the following:
Replaced chip with new one
turned on all PORTA , ignoring PINC
Buzzed out PWB to see if there were any stupid track faults
Tried another Board without switches fitted and tried manipulating the M16 legs
used PortB as Output
Pulled most my remaining hair

If I change code to read Port B and manipulate the pins, PortA follows PotrB.

Any suggestions what I have missed?
TIA
Matt

Tags:

Tools, Compilers and General Programming

JohanEkdahl

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Joined: Wed. Mar 27, 2002

Posts: 26945 View posts

Location: Lund, Sweden

Posted by JohanEkdahl: Fri. Oct 3, 2008 - 11:56 AM

The JTAG interface is on port C, and is enabled by default. Unprogram the JTAG fuse. Read more in the data sheet, sections "Alternate Portr Functions" and "Memory Programming".

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Matt_edwards

Level: Wannabe

Joined: Sat. Dec 14, 2002

Posts: 96 View posts

Location: Baulkham Hills, Australia

Posted by Matt_edwards: Fri. Oct 3, 2008 - 08:43 PM

JohanEkdahl wrote:

The JTAG interface is on port C, and is enabled by default.

Johan,
I read the data sheet. However obviously not understanding how the JTAG port would affect me. This is the first chip I have used with a JTAG. Thanks for your help.