H8S2245 datasheet(502/818 Pages) RENESAS

502 / 818 page

Section 12 Serial Communication Interface (SCI)

Rev.3.00 Mar. 26, 2007 Page 460 of 772

REJ09B0355-0300

In serial reception, the SCI operates as described below.

[1] The SCI performs internal initialization in synchronization with serial clock input or output.

[2] The received data is stored in RSR in LSB-to-MSB order.

After reception, the SCI checks whether the RDRF flag is 0 and the receive data can be

transferred from RSR to RDR.

If this check is passed, the RDRF flag is set to 1, and the receive data is stored in RDR. If a

receive error is detected in the error check, the operation is as shown in table 12.11.

Neither transmit nor receive operations can be performed subsequently when a receive error

has been found in the error check.

[3] If the RIE bit in SCR is set to 1 when the RDRF flag changes to 1, a receive data full interrupt

(RXI) request is generated.

Also, if the RIE bit in SCR is set to 1 when the ORER flag changes to 1, a receive error

interrupt (ERI) request is generated.

Figure 12.19 shows an example of SCI operation in reception.

Bit 7

Serial

data

Serial

clock

1 frame

RDRF

ORER

Bit 0

Bit 7

Bit 0

Bit 1

Bit 6

Bit 7

RXI interrupt request

generated

RDR data read and

RDRF flag cleared to 0

in RXI interrupt service

routine

RXI interrupt request

generated

ERI interrupt request

generated by overrun

error

Figure 12.19 Example of SCI Operation in Reception

Simultaneous serial data transmission and reception (clocked synchronous mode): Figure

12.20 shows a sample flowchart for simultaneous serial transmit and receive operations.

The following procedure should be used for simultaneous serial data transmit and receive

operations.

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