43.8.2 Transmit Operations

A transmit frame is triggered by a start event and can be followed by synchronization data before data transmission.

The start event is configured by setting the SSC_TCMR. See Start.

The frame synchronization is configured setting the Transmit Frame Mode Register (SSC_TFMR). See Frame Synchronization.

To transmit data, the transmitter uses a shift register clocked by the transmit clock signal and the start mode selected in the SSC_TCMR. Data is written by the application to the SSC_THR then transferred to the shift register according to the data format selected.

When both the SSC_THR and the transmit shift register are empty, the status flag TXEMPTY is set in the SSC_SR. When the Transmit Holding register is transferred in the transmit shift register, the status flag TXRDY is set in the SSC_SR and additional data can be loaded in the holding register.

Note: An unexpected delay on Transmit Data (TD) output may occur when the SSC is configured with the following conditions:
  • The START bit in the RCMR register = Start on falling edge/Start on Rising edge/Start on any edge
  • The FSOS bit in the RFMR register = None (input)
  • The START bit in the TCMR register = Receive Start

Under these conditions, an unexpected delay of two or three system clock cycles is added to the TD output.

Figure 43-11. Transmit Block Diagram