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Rev. 1.0, 07/01, page 217 of 372
14.7 Interrupts
SCI creates the following six interrupt requests: transmission end, transmit data empty, receive
data full, and receive errors (overrun error, framing error, and parity error). Table 14-6 shows the
interrupt sources.
Table 14-6 SCI Interrupt Requests
Interrupt Requests Abbrev. Interrupt Sources
Receive Data Full RXI Setting RDRF in SSR
Transmit Data Empty TXI Setting TDRE in SSR
Transmission End TEI Setting TEND in SSR
Receive Error ERI Setting OER, FER, and PER in SSR
The initial value of the TDRE flag in SSR is 1. Thus, when the TIE bit in SCR3 is set to 1 before
transferring the transmit data to TDR, a TXI interrupt request is generated even if the transmit data
is not ready. The initial value of the TEND flag in SSR is 1. Thus, when the TEIE bit in SCR3 is
set to 1 before transferring the transmit data to TDR, a TEI interrupt request is generated even if
the transmit data has not been sent. It is possible to make use of the most of these interrupt
requests efficiently by transferring the transmit data to TDR in the interrupt routine. To prevent
the generation of these interrupt requests (TXI and TEI), set the enable bits (TIE and TEIE) that
correspond to these interrupt requests to 1, after transferring the transmit data to TDR.