As explained in “comm_type”, depending on LON configuration the transmission may be terminated early upon collision notification which means that the DMA transfer may be stopped before its end.
In case of early end of transmission due to collision detection the USART in LON mode acts as follows:
- Send the end of frame trigger.
- Hold down TXRDY avoiding thus any additional DMA transfer.
- Set LTXD, LCOL and LFET flags in US_CSR.
- Wait that the application reconfigure the DMA.
- Wait until LCOL and LFET flags are cleared through US_CR. RSTSTA
(it releases the TXRDY signal).Figure 1. DMA, Collision and Early Frame Termination
