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CHAPTER 8 CLOCKED SERIAL INTERFACE UNIT (CSI)
User’s Manual U14272EJ3V0UM
159
8.2.3 CSI transfer types
(1) Burst mode
Burst mode is supported for both transmit and receive transfers. Burst lengths for transmission and reception are
independently programmable and can be set from 1 to 65535 bits. The transmit and receive shift registers are
both 8-bit lengths. During burst mode, when the receive shift register goes “full”, the data is automatically
transferred to the receive FIFO. When the transmit shift register goes “empty”, it is automatically reloaded from
the transmit FIFO.
Once the burst length has been set and the burst transaction enabled, the CSI behaves as follows:
The CSI begins tracking the number of bits transmitted and/or received. At the end of each bit transfer, the bit
count is updated and compared to the corresponding burst length value (transmit and/or receive). If the number
of bits transferred is equal to the burst length, the CSI shift register is halted.
If the transfer is a reception, the contents of the shift register will be copied to the receive FIFO, a Receive Burst
End interrupt request will be generated if unmasked, and additional activities on the SCK input will be ignored.
If the transfer is a transmission, a Transmit Burst End interrupt request will be generated if unmasked and
additional SCK cycles will cause an invalid data to be output on SO.
(2) Continuous mode
Continuous mode transfers are always defined as 8-bit fixed length transfers. In continuous mode, software must
control the flow of data between the V
R
4181 and the external master.
When continuous mode is enabled and the receive shift register goes “full”, the data is automatically transferred
to the receive FIFO. When the transmit shift register goes “empty”, it is automatically reloaded from the transmit
FIFO.