R8C/1A Group, R8C/1B Group 16. Clock Synchronous Serial Interface
Rev.1.30 Dec 08, 2006 Page 214 of 315
REJ09B0252-0130
16.3.3.3 Master Receive Operation
In master receive mode, the master device outputs the receive clock, receives data from the slave device, and
returns an acknowledge signal.
Figures 16.35 and 16.36 show the Operating Timing in Master Receive Mode (I
2
C bus Interface Mode).
The receive procedure and operation in master receive mode are shown below.
(1) After setting the TEND bit in the ICSR register to 0, switch from master transmit mode to master
receive mode by setting the TRS bit in the ICCR1 register to 0. Also, set the TDRE bit in the ICSR
register to 0.
(2) When performing the dummy read of the ICDRR register and starting the receive operation, the receive
clock is output in synchronization with the internal clock and data is received. The master device
outputs the level set by the ACKBT bit in the ICIER register to the SDA pin at the 9th clock cycle of the
receive clock.
(3) The 1-frame data receive is completed and the RDRF bit in the ICSR register is set to 1 at the rise of the
9th clock cycle. At this time, when reading the ICDRR register, the received data can be read and the
RDRF bit is set to 0 simultaneously.
(4) Continuous receive operation is enabled by reading the ICDRR register every time the RDRF bit is set
to 1. If the 8th clock cycle falls after the ICDRR register is read by another process while the RDRF bit
is set to 1, the SCL signal is fixed “L” until the ICDRR register is read.
(5) If the next frame is the last receive frame and the RCVD bit in the ICCR1 register is set to 1 (disables
the next receive operation) before reading the ICDRR register, stop condition generation is enabled
after the next receive operation.
(6) When the RDRF bit is set to 1 at the rise of the 9th clock cycle of the receive clock, generate the stop
condition.
(7) When the STOP bit in the ICSR register is set to 1, read the ICDRR register and set the RCVD bit to 0
(maintain the following receive operation).
(8) Return to slave receive mode.
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