Datasheet

Section 20 Serial Communication Interface 3 (SCI3, IrDA)
Page 724 of 982 REJ09B0465-0300 Rev. 3.00
Sep 17, 2010
H8S/20103, H8S/20203, H8S/20223, H8S/20115, H8S/20215, H8S/20235 Group
20.8 Interrupt Requests
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 20.8
shows the interrupt sources.
Table 20.8 SCI3 Interrupt Requests
Interrupt
Requests Abbreviation Interrupt Sources
DTC
Activation
Receive Data Full RXI Setting RDRF in SSR Possible
Transmit Data
Empty
TXI Setting TDRE in SSR Possible
Transmission End TEI Setting TEND in SSR Impossible
Receive Error ERI Setting OER, FER, and PER in SSR Impossible
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. The DTC can be activated to perform data
transfers with the TXI interrupt request. The TDRE flag is automatically cleared to 0 by the DTC
data transfer.
When the RDRF flag in SSR is set to 1, a RXI interrupt request is generated. When any of the
OER, PER and FER flags is set to 1, an ERI interrupt request is generated. The DTC can be
activated to perform data transfers with the RXI interrupt request. The RDRF flag is automatically
cleared to 0 by the DTC data transfer.
The TEI interrupt is generated if the TEND flag is set to 1 when the TEIE bit is 1. If the TEI and
TXI interrupts are generated at the same time, the TXI interrupt is accepted first. Therefore, if the
TDRE and TEND flags are to be simultaneously cleared in a TXI interrupt routine, branching to a
TEI interrupt routine cannot be performed.
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.