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Write to SPIDAT0 (SLAVE)
Write to SPIDAT1
SPICLK
SPISIMO
SPISOMI
SPIENA
SPICS
Write to SPIDAT1
Write to SPIDAT0 (SLAVE)
WORD1
WORD2
CSHOLD = 1
CSHOLD = 0
Operating Modes
1131
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Multi-Buffered Serial Peripheral Interface Module (MibSPI) with Parallel Pin
Option (MibSPIP)
Figure 24-13. Typical Diagram when a Buffer in Master is in CSHOLD Mode (SPI-SPI)
24.2.11.2 CSHOLD Bit in Slave Mode (Multi-buffered Mode)
If the CSHOLD bit in a buffer is set to 1, then the MibSPI does not wait for the SPICS pins to be de-
activated at the end of the shift operation to copy the received data to the receive RAM. With this feature,
it is possible for a slave in multi-buffer mode to do multiple data transfers without requiring the SPICS pins
to be deasserted between two buffer transfers.
If the CSHOLD bit in a buffer is cleared to 0 in a slave MibSPI, even after the shift operation is done, the
MibSPI waits until the SPICS pin (if functional) is deasserted to copy the received data to the RXRAM.
If the CSHOLD bit is maintained as 0 across all the buffers, then the slave in multi-buffer mode requires its
SPICS pins to be deasserted between any two buffer transfers; otherwise, the Slave SPI will be unable to
respond to the next data transfer.
NOTE:
In compatibility mode, the slave does not require the SPICS pin to be deasserted between
two buffer transfers. The CSHOLD bit of the slave will be ignored in compatibility mode.
24.2.12 Detection of Slave Desynchronization (Master Only)
When a slave supports generation of an enable signal (ENA), desynchronization can be detected. With
the enable signal a slave indicates to the master that it is ready to exchange data. A desynchronization
can occur if one or more clock edges are missed by the slave. In this case, the slave may block the SOMI
line until it detects clock edges corresponding to the next data word. This would corrupt the data word of
the desynchronized slave and the consecutive data word. A configurable 8-bit time-out counter
(T2EDELAY), which is clocked with SPICLK, is implemented to detect this slave malfunction. After the
transmission has finished (end of last bit transferred: either last data bit or parity bit) the counter is started.
If the ENA signal generated by the slave does not become inactive before the counter overflows, the
DESYNC flag is set and an interrupt is asserted (if enabled).