SPRUIV7B May 2022 – September 2023 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP
In full-duplex transmission, data is transmitted (shifted out serially on SPIDAT[0]) and received (shifted in serially on SPIDAT[1]) simultaneously on separate data lines.
The controller transmit-and-receive mode is programmable per channel (the MCSPI_CHCONF_0/1/2/3[13-12] TRM bit field).
Channel access to the shift registers for transmission/reception is based on the MCSPI_TX_0/1/2/3 transmitter register state, the MCSPI_RX_0/1/2/3 receiver register state, and round-robin arbitration.
Channels that meet the following rules are included in the round-robin list of active channels scheduled for transmission and/or reception. The arbiter skips channels that do not meet the rules and searches in the rotation for the next enabled channel.
When MCSPI word transfer completes (the MCSPI_CHSTAT_0/1/2/3[2] EOT bit is set), the updated MCSPI_TX_0/1/2/3 register of the next scheduled channel is loaded into the shift register. The serialization (transmit-and-receive) starts depending on the channel communication configuration. When serialization completes, the received data transfers to the channel receive register.
The serial clock (SPICLK) synchronizes shifting and sampling of the information on the two serial data lines (SPIDAT[0] and SPIDAT[1]). Each time a bit transfers out from the controller, 1 bit transfers in from the peripheral.
Figure 12-70 shows an example of a full-duplex system with a controller device on the left and a peripheral device on the right. After eight cycles of the serial clock SPICLK, WordA transfers from the controller to the peripheral. At the same time, WordB transfers from the peripheral to the controller.