Interrupts; Usage Notes; Break Detection And Processing; Table 14.6 Sci3 Interrupt Requests - Renesas H8 Series Hardware Manual

Section 14 Serial Communication Interface 3 (SCI3)
14.7

Interrupts

The SCI3 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 SCI3 Interrupt Requests

Interrupt Requests
Receive Data Full
Transmit Data Empty
Transmission End
Receive Error
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.
14.8

Usage Notes

14.8.1

Break Detection and Processing

When framing error detection is performed, a break can be detected by reading the RxD pin value
directly. In a break, the input from the RxD pin becomes all 0, setting the FER flag, and possibly
the PER flag. Note that as the SCI3 continues the receive operation after receiving a break, even if
the FER flag is cleared to 0, it will be set to 1 again.
Rev. 1.00 Aug. 28, 2006 Page 238 of 400
REJ09B0268-0100
Abbreviation Interrupt Sources
RXI Setting RDRF in SSR
TXI Setting TDRE in SSR
TEI Setting TEND in SSR
ERI Setting OER, FER, and PER in SSR