Peripheral registers

Most peripherals have an ENABLE register. Unless otherwise specified, the peripheral registers must be configured before enabling the peripheral.

PSEL registers must be set before a peripheral is enabled or started. Updating PSEL registers while the peripheral is running can cause undefined behavior. To connect a peripheral to a different GPIO, the following must be performed:

Disable the peripheral.
Update the PSEL register.
Re-enable the peripheral.

Note: The peripheral must be enabled before tasks and events can be used.

Most of the register values are not retained during System OFF or when a reset is triggered. Some registers will retain their values in System OFF or for some specific reset sources. These registers are marked as retained in the register description for a given peripheral. For more information on their behavior, see chapter RESET — Reset control.