Product Specs

Table Of Contents
32 SPIS Serial peripheral interface slave with
EasyDMA
Page
294
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,
that is, ORC (over-read) characters are not included in this number. 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.
Figure 74: SPI transaction when shortcut between END and ACQUIRE is enabled
32.4 Pin configuration
The CSN, SCK, MOSI, and MISO signals associated with the SPI slave are mapped to physical pins
according to the configuration specified in the PSEL.CSN, PSEL.SCK, PSEL.MOSI, and PSEL.MISO
registers respectively. If the CONNECT field of any of these registers is set to Disconnected, the associated
SPI slave signal will not be connected to any physical pins.
The PSEL.CSN, PSEL.SCK, PSEL.MOSI, and PSEL.MISO registers and their configurations are only used
as long as the SPI slave is enabled, and retained only as long as the device is in System ON mode, see
POWER Power supply on page 78 chapter for more information about power modes. When the peripheral
is disabled, the pins will behave as regular GPIOs, and use the configuration in their respective OUT bit field
and PIN_CNF[n] register. PSEL.CSN, PSEL.SCK, PSEL.MOSI, and PSEL.MISO must only be configured
when the SPI slave is disabled.
To secure correct behavior in the SPI slave, the pins used by the SPI slave must be configured in the GPIO
peripheral as described in Table 70: GPIO configuration before enabling peripheral on page 295 before
enabling the SPI slave. This is to secure that the pins used by the SPI slave are driven correctly if the SPI
SPI master can use the DEF
character to stop the transaction as
soon as possible if the transaction is
not granted.
Ignored
Ignored
Granted
0
0
1
2
0
1
2
DEF
DEF
DEF
DEF
A
B
C
CPU
Free
CPU
Free
SPIS
CPUPENDING
CPU
1
2
3
4
Lifeline
Semaphore assignment
MISO
MOSI
SCK
CSN
Transaction status
ACQUIRE
ACQUIRED
RELEASE
ACQUIRE
ACQUIRED
RELEASE
ACQUIRE
END
&
ACQUIRED