SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
The peripheral receive mode is programmable (set the MCSPI_CHCONF_0[13-12] TRM bit field to 0x1).
In receive-only mode, the MCSPI_TX_0 register must be loaded before the MCSPI is selected by an external MCSPI controller device. The MCSPI_TX_0 register content is always loaded into the shift register whether it is updated or not. The TX0_UNDERFLOW event is activated accordingly and does not prevent transmission.
When the MCSPI word transfer completes (the MCSPI_CHSTAT_0[2] EOT bit is set to 1), the received data is transferred to the channel receive register.
To use the MCSPI as a peripheral receive-only device, the TX0_EMPTY and TX0_UNDERFLOW interrupts and the DMA write requests must be disabled due to the state of the MCSPI_TX_0 register.
For a full-duplex transmission, the serial clock (SPICLK) synchronizes shifting and sampling of the information on the single serial data line. For full duplex, two data lines are required. If SPICLK synchronizes on a single serial data line, the data line should be half-duplex.
Figure 12-34 shows a half-duplex system with a controller device on the left and a receive-only peripheral device on the right. Each time a bit transfers out from the controller, 1 bit transfers in from the peripheral. After eight cycles of the serial clock SPICLK, WordA transfers from the controller to the peripheral.