SPRUJ17H March 2022 – October 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1
Single-buffer mode is selected when the MBUFMODE bit in SCIGCR1 is cleared to 0. In this mode, the SCI waits for data to be written to SCITD, transfers the data to SCITXSHF, and transmits the data. The TXRDY and TXEMPTY bits indicate the status of the transmit buffers. That is, when the transmitter is ready for data to be written to SCITD, the TXRDY bit is set. Additionally, if both SCITD and SCITXSHF are empty, then the TXEMPTY bit is also set.
You can transmit data by:
With the polling method, software can poll for the TXRDY bit to go high before writing the data to the SCITD register. The CPU is unnecessarily overloaded by selecting the polling method. To avoid this, you can use the interrupt or DMA method. To use the interrupt method, the SETTXINT bit is set. To use the DMA method, the SET_TX_DMA bit is set. Either an interrupt or a DMA request is generated the moment the TXRDY bit is set. When the SCI has completed transmission of all pending frames, the SCITXSHF register and SCITD are empty, the TXRDY bit is set, and an interrupt/DMA request is generated, if enabled. Because all data has been transmitted, the interrupt/DMA request must be halted. This can either be done by disabling the transmit interrupt (CLRTXINT) / DMA request (CLRTXDMA bit), or by disabling the transmitter (clear TXENA bit).
The TXRDY flag cannot be cleared by reading the corresponding interrupt offset in the SCIINTVECT0 or SCIINTVECT1 register.