Alternate functionality configuration of a GPIO pin

In alternate functionality mode, as the name indicates the pin will assign for other functionality.

Let’s discuss what precisely alternate function mode.

In the alternate function mode, as the name indicates, the pin will be assigned for alternate functionality. The alternate functionality can be anything like UART-TX, UART-RX, timers input channel or ADC’s input channel, etc…

From Figure1, the output control now actually driven by the alternate function output, not from the output which comes from the output data register. Here, the output data register has no control over the output control block.

When the I/O port is programmed as an alternate function as shown in Figure:

• The output buffer can configure as open-drain or push-pull.
• The output buffer will driven by signal coming from the peripheral.
• The Schmitt trigger input is activated.
• The weak pull-up and pull-down resistors are activated.
• The data present on the I/O pin sampled into the input data register every  AHB1 clock cycle.
• Read access to the input data register gets the I/O state.

In the following article, let’s see GPIO output speed register and its applicability.

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