spim_csx
108-031
spim_somi
spim_clk
Transmitter buffer
Shift register
Master
Control
Receiver register
Master SPI shift register
Initial
After 8
clock cycles
WordA
WordB
(single line)
Slave SPI shift register
Initial
After 8
clock cycles
WordB
WordC
Control
Slave
(transmit only)
Transmitter buffer
Shift register
Preliminary
Architecture
www.ti.com
12.2.4.5 Slave Transmit-Only Mode
The slave transmit only mode is programmable (bits TRM set to 10 in the register MCSPI_CH(I)CONF).
This mode avoids the CPU to read the receiver register (minimizing data movement) when only
transmission is meaningful.
To use McSPI as a slave transmit only device with (I)CONF[TRM]=00, the user should inhibit the
RX_full and RX_overflow interrupts and DMA read requests due to the receiver register sate.
On completion of SPI word transfer the bit EOT of the register MCSPI_CH(I)STAT is set. This bit is
meaningless when using the Buffer for this channel.
The built-in FIFO is available in this mode and can be configured with FFER bit field in the
MCSPI_CH(I)CONF register, then the FIFO is seen as a unique FFNBYTE bytes buffer.
shows a half-duplex system with a master device on the left and a transmit-only slave
device on the right. Each time a bit transfers out from the slave device, 1 bit transfers in the master.
After eight cycles of the serial clock spim_clk, WordB transfers from the slave to the master.
Figure 12-24. SPI Half-Duplex Transmission (Transmit-Only Slave)
12.2.5 Interrupts
According to its transmitter register state and its receiver register state each channel can issue interrupt
events if they are enabled.
The interrupt events are listed in the
and in
.
Each interrupt event has a status bit, in the MCSPI_IRQSTATUS register, which indicates service is
required, and an interrupt enable bit, in the MCSPI_IRQENABLE register, which enables the status to
generate hardware interrupt requests.
When an interrupt occurs and later a mask is applied on it (IRQENABLE), the interrupt line is not
asserted again even if the interrupt source has not been serviced.
McSPI supports interrupt driven operation and polling.
1244
Multichannel Serial Port Interface (McSPI)
SPRUGX9 – 15 April 2011
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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