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13.8
Interrupt Sources
13.8.1
Interrupts in Normal Serial Communication Interface Mode
Table 13.12 shows the interrupt sources in normal serial communication interface mode. A
different interrupt vector is assigned to each interrupt source, and individual interrupt sources can
be enabled or disabled using the enable bits in SCR.
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 request can activate the
DTC to allow data transfer. The TDRE flag is automatically cleared to 0 at data transfer by the
DTC.
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 allow data transfer. The RDRF flag is automatically cleared to 0 at data
transfer by the DTC.
A TEI interrupt is requested when the TEND flag is set to 1 while the TEIE bit is set to 1. If a TEI
interrupt and a TXI interrupt are requested simultaneously, the TXI interrupt has priority for
acceptance. However, note that if the TDRE and TEND flags are cleared to 0 simultaneously by
the TXI interrupt processing routine, the SCI cannot branch to the TEI interrupt processing routine
later.
Table 13.12 SCI Interrupt Sources
Name
Interrupt Source
ERI
Receive error
RXI
Receive data full
TXI
Transmit data empty
TEI
Transmit end
Section 13 Serial Communication Interface (SCI)
Interrupt Flag
ORER, FER, or PER
RDRF
TDRE
TEND
DTC Activation
Not possible
Possible
Possible
Not possible
Rev.2.00 Jun. 28, 2007 Page 517 of 666
REJ09B0311-0200
Priority
High
Low
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