NRF52820-QDAA-R datasheet(86/437 Pages) NORDIC

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Peripherals

6.1.2 Peripherals with shared ID

In general (with the exception of ID 0), peripherals sharing an ID and base address may not be used

simultaneously. The user can only enable one peripheral at the time on this specific ID.

When switching between two peripherals sharing an ID, the user should do the following to prevent

unwanted behavior:

1. Disable the previously used peripheral.

2. Remove any programmable peripheral interconnect (PPI) connections set up for the peripheral that is

being disabled.

3. Clear all bits in the INTEN register, i.e. INTENCLR = 0xFFFFFFFF.

4. Explicitly configure the peripheral that you are about to enable and do not rely on configuration values

that may be inherited from the peripheral that was disabled.

5. Enable the now configured peripheral.

See which peripherals are sharing ID in Instantiation on page 18.

6.1.3 Peripheral registers

Most peripherals feature an ENABLE register. Unless otherwise specified in the relevant chapter, the

peripheral registers (in particular the PSEL registers) must be configured before enabling the peripheral.

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

6.1.4 Bit set and clear

Registers with multiple single-bit bit fields may implement the set-and-clear pattern. This pattern enables

firmware to set and clear individual bits in a register without having to perform a read-modify-write

operation on the main register.

This pattern is implemented using three consecutive addresses in the register map, where the main

The SET register is used to set individual bits in the main register while the CLR register is used to clear

individual bits in the main register. Writing

1 to a bit in SET or CLR register will set or clear the same bit in

the main register respectively. Writing

0 to a bit in SET or CLR register has no effect. Reading the SET or

CLR register returns the value of the main register.

Note: The main register may not be visible and hence not directly accessible in all cases.

6.1.5 Tasks

Tasks are used to trigger actions in a peripheral, for example to start a particular behavior. A peripheral can

implement multiple tasks with each task having a separate register in that peripheral's task register group.

A task is triggered when firmware writes

1 to the task register, or when the peripheral itself or another

peripheral toggles the corresponding task signal. See Tasks, events, shortcuts, and interrupts on page

85.

6.1.6 Events

Events are used to notify peripherals and the CPU about events that have happened, for example a state

change in a peripheral. A peripheral may generate multiple events with each event having a separate

An event is generated when the peripheral itself toggles the corresponding event signal, and the event

interrupts on page 85. An event register is only cleared when firmware writes

0 to it.

4463_156 v1.0

NRF52820-QDAA-R Datasheet(PDF) 86 Page - Nordic Semiconductor

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