Texas Instruments OMAP5912 Reference Manual page 1116

Figure 14. Example of an Underflow Generation With CIi = 0, CEi = 0 and CPi = 0
DMA read on SPI_RX
DMA write
SPI_TX
SPI_CTRL
SPEN0
1
SRCLK
SPI_SR
dNB
TSPDO
dNB
TSPDI
TSPDOEN
IRQ
RX_ndma_req
TX_ndma_req
SPI_ISR
RE = 0; WE = 0
SPI_DSR TX_EMPTY = 0
SPI_RX
SPRU760B
MCU-DSP write in SPI_ISR
WRITE DATA 1
NB+1
READ DATA 1
d0
d0
2 OCP clock cycles
RE = 1;
RE = 0
WE = 1
READ DATA 1
MCU-DSP write in SPI_ISR
DMA read on SPI_RX
RD = 1; WR = 1
NB+1
1
dNB
d0
dNB
d0
RE = 1
TX_underflow = 1
TX_EMPTY = 1
SPI Master/Slave
DMA write on SPI_TX
MCU-DSP write
in SPI_ISR
READ DATA 2
2 OCP clock cycles
WE = 0;
RE = 0
TX_overflow = 0
TX_EMPTY = 0
READ DATA 2
Serial Interfaces 51