SH7144_08 Datasheet, PDF (563/930 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family/SH7144 Series

14. I²C Bus Interface (IIC) Option
In the slave transmit mode, the slave device transmits data while the master device outputs the
receive clock and returns acknowledgements of reception. The following description gives the
procedures for and operations of transmitting in slave transmit mode.
1. Perform initialization of slave receive mode and wait for slave address reception.
2. When the slave address matches the address in the first frame following the start condition
detection, the slave device drives SDA to low at the 9th cycle of the clock and returns
acknowledgement. When the 8th bit of data (R/W) is 1, the TRS bit is set to 1 and slave
transmit mode is automatically entered. The IRIC flag is set to 1 at the rising edge of the 9th
cycle of the clock. At this time, if the IEIC bit is set to 1, an interrupt request is generated for
the CPU. The ICDRE flag is set to 1. The slave device keeps SCL low to prevent the master
device from outputting the next transmit clock from the falling edge of the 9th cycle of the
transmit clock until data is written to ICDR.
3. After the IRIC flag is cleared to 0, the transmit data is written to ICDR. In this case, the
ICDRE flag is cleared to 0. The written data is transferred to ICDRS, and the ICDRE and IRIC
flags are again set to 1. The slave device sequentially transmits the data transferred to ICDRS,
on the basis of the clock from the master device.
To detect the completion of transmission, clear the IRIC flag to 0. After writing the ICDR
register, sequentially clear the IRIC flag so that no other process is inserted.
4. The master device drives SDA to low at the 9th cycle of the transfer frame and returns the
acknowledgement. Since the acknowledgement is stored in the ACKB bit in ICSR, it can be
checked whether transfer operation is performed normally. One frame of data transmission is
completed and the IRIC flag is set to 1 at the rising edge of the 9th cycle of the transmit clock.
When the ICDRE flag is 0, data written to the ICDR is transferred to ICDRS and one frame of
data transmission is started, and then the ICDRE and IRIC flags are again set to 1. If the
ICDRE flag is set to 1, SCL is kept low from the falling edge of the 9th cycle of the transmit
clock until the data is written to the ICDR.
5. To continue with the transmission, write the next data for transmission to ICDR. In this case,
the ICDRE flag is cleared to 0. To detect the completion of transmission, clear the IRIC flag to
0. Perform the ICDR register writing and the IRIC flag clearing sequentially so that no other
process is inserted.
Transmission can be continued by repeating steps 4 and 5.
6. Clear the IRIC flag to 0.
7. To end the transmission, clear the ACKE bit in ICCR and the acknowledge bit stored in the
ACKB bit to 0.
8. For the next address reception, clear the TRS bit to 0 and enter slave receive mode.
9. To release SDA on the slave side, dummy read ICDR.
Rev.4.00 Mar. 27, 2008 Page 519 of 882
REJ09B0108-0400