2313 output pin problem

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Hi all,

I'm just starting out with the AVR series of uc's. I've successfully
built a programmer of the "alf" type, and verified that it works properly.

So here's my simple program:

void main(void)
{
	DDRB = 0xff; // port b set to all outputs
	PORTB = 0;
}

I have a 220-ohm resistor and an LED hooked up in series between VCC (5
volts) and PB7, which is also the SCK pin. I know the LED is connected
the right way, because it lights up during programming. So the above
program should drive PB7 to ground, thus lighting the LED.

But when I run the program, the LED doesn't light up. All the other port
B pins are at 0 volts, but PB7 is at 3.75 volts, almost as if the pin
were floating, which can't be right, or am I reading the data sheet wrong?

I also changed PORTB to 0xff and verified that all the pins are at 5 volts.

So what's wrong? I'd appreciate any help.

Thanks!

- --Rob

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