HD64F2149 Datasheet, PDF (504/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

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
Interrupt
Channel 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.
The TEI interrupt is requested when the TEND flag is set to 1 while the TEIE bit is set to 1. The
TEND flag is cleared at the same time as the TDRE flag. Consequently, if a TEI interrupt and a
TXI interrupt are requested simultaneously, the TXI interrupt will have priority for acceptance,
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