Texas Instruments OMAP5912 Reference Manual page 1094

1.4.1 MCU-DSP Protocol
MCU-DSP Transmit Protocol in Master Mode
SPRU760B
The host is either the MCU or the DSP.
The protocol has several steps:
Step 1: MCU-DSP writes to the setup registers (SPI_SET1 and SPI_SET2).
Step 2: MCU-DSP writes to the transmit register (SPI_TX).
Step 3: MCU-DSP writes to the control register (SPI_CTRL).
Once the WR bit is set:
The transmit register (SPI_TX) is copied into the shift register
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(SPI_SR).
The device enable goes low (nTSPENi), if CEi = 0 in SPI_SET2.
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The shift register clock is activated (SRCLK) and the transmis-
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sion starts.
One SRCLK cycle later, the WR bit is reset.
Step 4: When the transmission is completed:
The device enable (nTSPENi) goes high if CEi = 0 in SPI_SET2.
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The WE bit is set in the interrupt status register (SPI_ISR).
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An interrupt is generated, if MSK1 is set in the interrupt enable
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register (SPI_IER).
Step 5: Once the MCU-DSP clears the WE status bit (SPI_ISR), the interrupt
request is released.
SPI Master/Slave
Serial Interfaces 29