R8C/1A Group, R8C/1B Group
16. Clock Synchronous Serial Interface
Rev.1.30
Dec 08, 2006
Page 220 of 315
REJ09B0252-0130
16.3.3.5
Slave Receive Operation
In slave receive mode, the master device outputs the transmit clock and data, and the slave device returns an
acknowledge signal.
Figures 16.39 and 16.40 show the Operating Timing in Slave Receive Mode (I
2
C bus Interface Mode).
The receive procedure and operation in slave receive mode are as follows.
(1) Set the ICE bit in the ICCR1 register to 1 (transfer operation enabled). Set bits WAIT and MLS in the
ICMR register and bits CKS0 to CKS3 in the ICCR1 register (initial setting). Set bits TRS and MST in
the ICCR1 register to 0 and wait until the slave address matches in slave receive mode.
(2) When the slave address matches at the 1st frame after detecting the start condition, the slave device
outputs the level set in the ACKBT bit in the ICIER register to the SDA pin at the rise of the 9th clock
cycle. Since the RDRF bit in the ICSR register is set to 1 simultaneously, perform the dummy-read (the
read data is unnecessary because if indicates the slave address and R/W).
(3) Read the ICDRR register every time the RDRF bit is set to 1. If the 8th clock cycle falls while the
RDRF bit is set to 1, the SCL signal is fixed “L” until the ICDRR register is read. The setting change of
the acknowledge signal returned to the master device before reading the ICDRR register takes affect
from the following transfer frame.
(4) Reading the last byte is performed by reading the ICDRR register in like manner.
