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Mini57
Apr. 06, 2017
Page 355 of 475
Rev.1.00
MINI5
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is set to 1, the SPI Slave will be ready to transmit/receive data after the SPI protocol is enabled by
setting FUNMODE(USPI_CTL [2:0]) to 0x1.
6.13.5.9 Data Transfer Mode
The USCI controller supports full-duplex SPI transfer.
In full-duplex SPI transfer, there are two data pins. One is used for transmitting data and the other
is used for receiving data. Thus, data transmission and data reception can be performed
simultaneously.
SCLKMODE (USPI_PROTCTL[7:6]) defines the transition timing of the data shift output signal on
USCIx_DAT0 pin. The transition may happen at the corresponding edge of SPI bus clock or
active edge of slave select signal. The level of the last data bit of a data word is held on
USCIx_DAT0 pin until the next data word begins with the next corresponding edge of the serial
bus clock.
6.13.5.10 Interrupt
Data Transfer Interrupts
Transmit start interrupt
The interrupt event TXSTIF (USPI_PROTSTS[1]) is set after the start of the first data bit of a
transmit data word. It can be cleared only by writing 1 to it. The controller wil issue an interrupt if
TXSTIEN (USPI_INTEN[1]) is also set to 1.
Transmit end interrupt
The interrupt event TXENDIF (USPI_PROTSTS[2]) is set after the start of the last data bit of the
last transmit data which has been stored in transmit buffer. It can be cleared only by writing 1 to it.
The controller wil issue an interrupt if TENDIEN (USPI_INTEN[2]) is also set to 1.
Receive start interrupt
The interrupt event RXSTIF (USPI_PROTSTS[3]) is set after the start of the first data bit of a
receive data word. It can be cleared only by writing 1 to it. The controller wil issue an interrupt if
RXSTIEN (USPI_INTEN[3]) is also set to 1.
Receive end interrupt
The interrupt event RXENDIF (USPI_PROTSTS[4]) is set after the start of the last data bit of a
receive data word. It can be cleared only by writing 1 to it. The controller wil issue an interrupt if
RXENDIEN (USPI_INTEN[4]) is also set to 1.
Protocol-Related Interrupts
SPI slave select interrupt
In SPI slave mode, there are slave select active and in-active interrupt flags, SSACTIF
(USPI_PROTSTS[9]) and SSINAIF (USPI_PROTSTS[8]), will be set to 1 when SLAVE
(USPI_PROTCTL [0]) is set to 1 and slave senses the slave select signal active or inactive. The
SPI controller will issue an interrupt if SSINAIEN (USPI_PROTIEN[0]) or SSACTIEN
(USPI_PROTIEN[1]), are set to 1. Because the internal slave select signal in SPI function is
active high, the ININV (USPI_CTLIN0[2]) can be used for inverting the slave select signal comes
from an active low device.