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10. Serial Communication Interface
Continuous Transmit/Receive Operation Using Interrupts: Continuous transmit and receive
operations are possible with SCI3, using the RXI or TXI interrupts. Table 10.13 explains this use
of these interrupts.
Table 10.13 Transmit/Receive Interrupts
Interrupt
Flag
RXI
RDRF
RIE
TXI
TDRE
TIE
TEI
TEND
TEIE
RDR
RSR (receiving)
RXD
pin
RDRF = 0
Rev.3.00 Jul. 19, 2007 page 282 of 532
REJ09B0397-0300
Interrupt Conditions
When serial data is received normally
and receive data is transferred from
RSR to RDR, RDRF is set to 1. If RIE
is 1 at this time, RXI is enabled and an
interrupt occurs. (See figure
10.4.)
When TSR empty (previous trans-
mission complete) is detected and the
transmit data set in TDR is transferred
to TSR, TDRE is set to 1. If TIE is 1 at
this time, TXI is enabled and an
interrupt occurs. (See figure 10.5.)
When the last bit of the TSR transmit
character has been sent, if TDRE is 1,
then 1 is set in TEND. If TEIE is 1 at
this time, TEI is enabled and an
interrupt occurs. (See figure 10.6.)
Figure 10.4 RDRF Setting and RXI Interrupt
Remarks
The RXI interrupt handler routine
should read the receive data from
RDR and clear RDRF to 0.
Continuous receiving is possible if
these operations are completed
before the next data has been
completely received in RSR.
The TXI interrupt handler routine
should write the next transmit data
to TDR and clear TDRE to
0.Continuous transmission is
possible if these operations are
completed before the data
transferred to TSR has been
completely transmitted.
TEI indicates that, when the last bit
of the TSR transmit character was
sent, the next transmit data had
not been written to TDR.
RDR
↑
RSR
(received and transferred)
RXD
pin
RDRF
(RXI requested if RIE = 1)
←
1
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