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How Are Promira Serial Platform Pins Configured? Do I Need to Add Pull-Up Resistors?
Rena Ayeras

Question from the Customer:

Can you tell me about the pin configuration of pin 14 and pin 15 of the Promira Serial Platform? I am using these two pins as DO. Are they both open-collector pins – will I need to add pull-up resistors?

Response from Technical Support:

Thanks for your questions! The I/O circuit depends on how you are using the Promira Serial Platform.


Promira Serial Platform can be used with I2C and SPI devices Promira Serial Platform

The I/O Circuit for I2C Slave Configuration

The Promira platform when used as an I2C slave has 560 Ohm internal pull-up resistors that cannot be turned off.  As I2C devices are open collector, the I2C master should sink at least 10mA.

The I/O Circuit for SPI Configuration

The I/O circuit on pins 14 and 15 depends on how the pins are configured.

SPI Chip Select Pins

When pins 14 and 15 are configured as SPI chip selects, they are “push-pull” - driven by the Promira platform


When pins 14 and 15 are configured as GPIO:

  • When GPIO is an output pin, it is “push-pull”.  In this case, the pin is driven by the Promira platform
  • When GPIO is an input pin, it is “tri-stated”. In this case, the pin behaves as an open-collector

Note: the Promira platform already has internal 2.2k pull-up resistors on these lines – you should not need to add external pull-up resistors.

We hope this answers your question. Additional resources that you may find helpful include the following:

More questions? Other projects? You can also contact us at sales@totalphase.com. You can also request a demo that applies to your application.

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