Table 14-9 SCI Interrupts
DTC Service
Interrupt Description Available? Priority
ERI Receive-error interrupt, requested when No High
ORER, FER, or PER is set.
RXI Receive-end interrupt, requested when Yes
RDRF is set.
TXI Transmit-end interrupt, requested when Yes
TDRE is set.
Low
The TXI and RXI interrupts can be served by the data transfer controller (DTC) to have a data
transfer performed. When the DTC serves one of these interrupts, it clears the TDRE or RDRF bit
to 0 under the following conditions, which differ between the two bits.
When invoked by a TXI request, if the DTC writes to the TDR, it automatically clears the TDRE
bit to 0. When invoked by an RXI request, if the DTC reads from the RDR, it automatically clears
the RDRF bit to 0.
See section 6, “Data Transfer Controller” for further information on the DTC.
14.5 Application Notes
Application programmers should note the following features of the SCI.
1. TDR Write: The TDRE bit in the SSR is simply a flag that indicates that the TDR contents
have been transferred to the TSR. The TDR contents can be rewritten regardless of the TDRE
value. If a new byte is written in the TDR while the TDRE bit is 0, before the old TDR
contents have been moved into the TSR, the old byte will be lost. Normally, software should
check that the TDRE bit is set to 1 before writing to the TDR.
2. Multiple Receive Errors: Table 14-10 lists the values of flag bits in the SSR when multiple
receive errors occur, and indicates whether the RSR contents are transferred to the RDR.
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