488
13.4 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 13-12 shows the interrupt sources and their relative priorities. Individual interrupt
sources can be enabled or disabled with the TIE, RIE, and TEIE bits in the 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 13-12 SCI Interrupt Sources
Channel
Interrupt
Source Description
DTC
Activation Priority*
0 ERI Interrupt due to receive error (ORER, FER, or PER) Not possible High
RXI Interrupt due to receive data full state (RDRF) Possible
TXI Interrupt due to transmit data empty state (TDRE) Possible
TEI Interrupt due to transmission end (TEND) Not possible
1 ERI Interrupt due to receive error (ORER, FER, or PER) Not possible
RXI Interrupt due to receive data full state (RDRF) Possible
TXI Interrupt due to transmit data empty state (TDRE) Possible
TEI Interrupt due to transmission end (TEND) Not possible
2
(H8S/2648,
ERI Interrupt due to receive error (ORER, FER, or PER) Not possible
H8S/2648R,
H8S/2647)
RXI Interrupt due to receive data full state (RDRF) Possible
TXI Interrupt due to transmit data empty state (TDRE) Possible
TEI Interrupt due to transmission end (TEND) Not possible Low
Note: *This table shows the initial state immediately after a reset. Relative priorities among
channels can be changed by means of the interrupt controller.
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