Insufficient voltage level on general io output pin

[Amy]

Hi!

I am using an Adapt9s12e128 (for Motorola MC9S12E128) from
Technological Arts without BDM.

I am trying to use PORT Q as outputs to control LEDs. PMF is disabled.
However, I am having some problem with bit 6 of this port.

If I set every bit in this port(Q6-Q0) to 1, with Metrowerks' real
time debugger, I can see PORT Q I/O register PTQ is 0x7F. However,
PORT Q input register PTIQ shows 0x3F. And if I measure the voltage at
this pin, it's 1.35V instead of 5V.

It works normally when set to 0.

I checked on the schematics of Adapt9s12e128 and nothing is connected
to this pin.

What could be the cause of this?

Any comments/help is greatly appreciated!

Amy

 

[CBFalconer]

I am using an Adapt9s12e128 (for Motorola MC9S12E128) from
Technological Arts without BDM.

I am trying to use PORT Q as outputs to control LEDs. PMF is disabled.
However, I am having some problem with bit 6 of this port.

If I set every bit in this port(Q6-Q0) to 1, with Metrowerks' real
time debugger, I can see PORT Q I/O register PTQ is 0x7F. However,
PORT Q input register PTIQ shows 0x3F. And if I measure the voltage at
this pin, it's 1.35V instead of 5V.

It works normally when set to 0.

I checked on the schematics of Adapt9s12e128 and nothing is connected
to this pin.

What could be the cause of this?

Is it an open collector (drain) without a pullup resistor?