NRF52820-QDAA-R datasheet(266/437 Pages) NORDIC

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Peripherals

If the CPU tries to acquire the semaphore while it is assigned to the SPI slave, an immediate handover

will not be granted. However, the semaphore will be handed over to the CPU as soon as the SPI slave

has released the semaphore after the granted transaction is completed. If the END_ACQUIRE shortcut

is enabled and the CPU has triggered the ACQUIRE task during a granted transaction, only one ACQUIRE

request will be served following the END event.

The MAXRX register specifies the maximum number of bytes the SPI slave can receive in one granted

transaction. If the SPI slave receives more than MAXRX number of bytes, an OVERFLOW will be indicated

in the STATUS register and the incoming bytes will be discarded.

The MAXTX parameter specifies the maximum number of bytes the SPI slave can transmit in one granted

transaction. If the SPI slave is forced to transmit more than MAXTX number of bytes, an OVERREAD will be

indicated in the STATUS register and the ORC character will be clocked out.

The RXD.AMOUNT and TXD.AMOUNT registers are updated when a granted transaction is completed. The

TXD.AMOUNT register indicates how many bytes were read from the TX buffer in the last transaction. This

does not include the ORC (over-read) characters. Similarly, the RXD.AMOUNT register indicates how many

bytes were written into the RX buffer in the last transaction.

The ENDRX event is generated when the RX buffer has been filled.

DEF

CPU

Free

CPUPENDING

CPU

Ignored

Granted

Ignored

DEF

CPU

Free

DEF

SPI master can use the DEF

character to stop the transaction as

soon as possible if the transaction is

not granted.

DEF

SPIS

Figure 103: SPI transaction when shortcut between END and ACQUIRE is enabled

4463_156 v1.0

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NRF52820-QDAA-R Datasheet(PDF) 266 Page - Nordic Semiconductor