R8CSLASH20 datasheet(352/501 Pages) RENESAS

352 / 501 page

R8C/20 Group, R8C/21 Group

16. Clock Synchronous Serial Interface

Rev.2.00 Aug 27, 2008

Page 336 of 458

REJ09B0250-0200

16.3.4.2

Transmit Operation

In transmit mode, transmit data is output from the SDA pin synchronizing with the fall 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 16.42 shows the Operating Timing in Transmit Mode (Clock Synchronous Serial Mode).

The transmit procedure and operation in transmit mode are shown below.

(1) Set the ICE bit in the ICCR1 register to 1 (transfer operation enabled). Set the CKS0 to CKS3 bits 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 the ICDRT to ICDRS registers 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. When writing

data to the ICDRT register every time the TDRE bit is set to 1, the continuous transmit is enabled. When

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

Figure 16.42

Operating Timing in Transmit Mode (Clock Synchronous Serial Mode)

SDA

(output)

SCL

ICDRT register

ICDRS register

Process

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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