R28 datasheet(323/473 Pages) RENESAS

323 / 473 page

R8C/28 Group, R8C/29 Group

16. Clock Synchronous Serial Interface

Rev.2.10

Sep 26, 2008

Page 304 of 441

REJ09B0279-0210

16.3.4.2

Transmit Operation

In transmit mode, transmit data is output from the SDA pin in synchronization with the falling edge of the

transfer clock. The transfer clock is output when the MST bit in the ICCR1 register is set to 1 and input when

the MST bit is set to 0.

Figure 16.41 shows the Operating Timing in Transmit Mode (Clock Synchronous Serial Mode).

The transmit procedure and operation in transmit mode are as follows.

(1) Set the ICE bit in the ICCR1 register to 1 (transfer operation enabled). Set bits CKS0 to CKS3 in the

ICCR1 register and set the MST bit (initial setting).

(2) The TDRE bit in the ICSR register is set to 1 by selecting transmit mode after setting the TRS bit in the

ICCR1 register to 1.

(3) Data is transferred from registers ICDRT to ICDRS and the TDRE bit is automatically set to 1 by

writing transmit data to the ICDRT register after confirming that the TDRE bit is set to 1. Continuous

transmission is enabled by writing data to the ICDRT register every time the TDRE bit is set to 1. When

switching from transmit to receive mode, set the TRS bit to 0 while the TDRE bit is set to 1.

Figure 16.41

Operating Timing in Transmit Mode (Clock Synchronous Serial Mode)

SDA

(output)

SCL

ICDRT register

ICDRS register

Processing

by program

TDRE bit in

ICSR register

TRS bit in

ICCR1 register

Data 1

Data 2

Data 3

Data 1

Data 2

Data 3

(2) Set TRS bit to 1

(3) Data write to

ICDRT register

(3) Data write to

ICDRT register

(3) Data write to

ICDRT register

(3) Data write to

ICDRT register

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