Table of Contents
Advertisement
17.5.5
Slave Transmit Operation
In slave transmit mode, the slave device outputs the transmit data, while the master device outputs
the receive clock and returns an acknowledge signal. The transmission procedure and operations in
slave transmit mode are described below.
1. Set the ICE bit in ICCR to 1. Set the MLS bit in ICMR and the MST and TRS bits in ICCR
according to the operating mode.
2. When the slave address matches in the first frame following detection of the start condition,
the slave device drives SDA low at the 9th clock pulse and returns an acknowledge signal. At
the same time, the IRIC flag in ICCR is set to 1. If the IEIC bit in ICCR has been set to 1, an
interrupt request is sent to the CPU. If the 8th data bit (R/W) is 1, the TRS bit in ICCR is set to
1, and the mode changes to slave transmit mode automatically. The TDRE internal flag is set
to 1. The slave device drives SCL low from the fall of the transmit clock until ICDR data is
written.
3. After clearing the IRIC flag to 0, write data to ICDR. The TDRE internal flag is cleared to 0.
The written data is transferred to ICDRS, and the TDRE internal flag and IRIC and IRTR flags
are set to 1 again. After clearing the IRIC flag to 0, write the next data to ICDR. The slave
device sequentially sends the data written into ICDR in accordance with the clock output by
the master device at the timing shown in figure 17.12.
4. When one frame of data has been transmitted, the IRIC flag in ICCR is set to 1 at the rise of
the 9th transmit clock pulse. If the TDRE internal flag has been set to 1, this slave device
drives SCL low from the fall of the transmit clock until data is written to ICDR. The master
device drives SDA low at the 9th clock pulse, and returns an acknowledge signal. As this
acknowledge signal is stored in the ACKB bit in ICSR, this bit can be used to determine
whether the transfer operation was performed normally. When the TDRE internal flag is 0, the
data written into ICDR is transferred to ICDRS and the TDRE internal flag and IRIC and
IRTR flags are set to 1 again.
5. To continue transmission, clear the IRIC flag to 0, then write the next data to be transmitted
into ICDR. The TDRE internal flag is cleared to 0.
Transmit operations can be performed continuously by repeating steps [4] and [5]. To end
transmission, write H'FF to ICDR. When SDA is changed from low to high when SCL is high and
the stop condition is detected, the BBSY flag in ICCR is cleared to 0.
2
Section 17 I
C Bus Interface (IIC)
Rev. 3.00 Jan 25, 2006 page 525 of 872
REJ09B0286-0300
Advertisement
Table of Contents
