Insufficient voltage level on general io output pin

- A
- Amy
  
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posted
19 years ago

Thu, Sep 2, 2004 8:13 PM

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

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- C
- CBFalconer
  
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Vote on answer
posted
19 years ago

Fri, Sep 3, 2004 2:17 AM

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

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