442
15.4
SCI Interrupts
The SCI has four interrupt sources: the transmit-end interrupt (TEI) request, receive-error
interrupt (ERI) request, receive-data-full interrupt (RXI) request, and transmit-data-empty
interrupt (TXI) request. Table 15.13 shows the interrupt sources and their relative priorities.
Individual interrupt sources can be enabled or disabled with the TIE, RIE, and TEIE bits in SCR.
Each kind of interrupt request is sent to the interrupt controller independently.
When the TDRE flag in SSR is set to 1, a TXI interrupt request is generated. When the TEND
flag in SSR is set to 1, a TEI interrupt request is generated. A TXI interrupt can activate the
DTC to perform data transfer. The TDRE flag is cleared to 0 automatically when data transfer is
performed by the DTC. The DTC cannot be activated by a TEI interrupt request.
When the RDRF flag in SSR is set to 1, an RXI interrupt request is generated. When the ORER,
PER, or FER flag in SSR is set to 1, an ERI interrupt request is generated. An RXI interrupt can
activate the DTC to perform data transfer. The RDRF flag is cleared to 0 automatically when
data transfer is performed by the DTC. The DTC cannot be activated by an ERI interrupt
request.
Table 15.13 SCI Interrupt Sources
Channel
Interrupt
Source
Description
DTC Activation
Priority*
0
ERI
Receive error (ORER, FER, or PER)
Not possible
High
RXI
Receive data register full (RDRF)
Possible
TXI
Transmit data register empty (TDRE)
Possible
TEI
Transmit end (TEND)
Not possible
1
ERI
Receive error (ORER, PER, or PER)
Not possible
RXI
Receive data register full (RDRF)
Possible
TXI
Transmit data register empty (TDRE)
Possible
TEI
Transmit end (TEND)
Not possible
2
ERI
Receive error (ORER, PER, or PER)
Not possible
RXI
Receive data register full (RDRF)
Possible
TXI
Transmit data register empty (TDRE)
Possible
TEI
Transmit end (TEND)
Not possible
Low
Note: * The table shows the initial state immediately after a reset. Relative channel priorities can
be changed by the interrupt controller.