TAS1020B data direction for GPIO pins

Rich B

Morning all

I'm currently working with a TAS1020B, which is an 8051/8052 derivative.

After much glaring through the imho inadequate sections of the datasheet on GPIO, i'm still left unsure of how to set the data direction per pin of a GPIO bank.

Can someone help me out? Clearly writing 1 or 0 to a bit in P1 or P3 will raise and lower the level of the respective pin, but how does one make a pin into an input?

I cant seem to find what i'm looking for in the datasheet, or any other 8051/2 documentation. Must be missing something...

Thanks in advance

Rich

over 16 years ago

0 Rich B over 16 years ago

Prodigy 110 points

I've solved my problem with help of a hardware engineer.

Rich

0 Don Dapkus over 16 years ago in reply to Rich B

TI__Guru**** 189401 points

Hey, Rich,

Sorry our documentation wasn't very clear in that regard.

Hey, in the spirit of community helping others, can you post how you solved this?

-d2

0 Rich B over 16 years ago in reply to Don Dapkus

Prodigy 110 points

Sure...

The GPIO in this device isn't as I (wrongly) assumed it to be. There is no register associated with each P0, P1, ... register which selects whether a GPIO pin is an output or an input pin.

When one writes a 1 to a GPIO register bit, and the circuit is wired correctly, instructions that follow can read the state of the pin. This is because the writing to the registers is completely separate from the reading of them; reading does not imply that you read the value you wrote to the register.

This is my understanding from a software viewpoint, hope this helps someone.

Rich

0 Don Dapkus over 16 years ago in reply to Rich B

TI__Guru**** 189401 points

thx!

0 Dana Myers over 16 years ago in reply to Rich B

Intellectual 270 points

That's traditionally how MCS-51 family ports work; Intel called it "quasi-bi-directional". Writing a 1 to a pin basically turns on a pull-up resistor, then you can read the state of the pin.

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TAS1020B data direction for GPIO pins