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Rev. 2.0, 09/02, page 415 of 732
The TDRE and RDRF flags are set/cleared under the following conditions. The setting of these
flags affects the state of the interrupt flag.
TDRE
Description
0
Transmission cannot be started or the next datum for transmission is present in the
ICDR (ICDRT).
[Clearing conditions]
(Initial Condition)
(1) In the transmission mode (TRS = 1), writing of a datum for transmission to ICDR
(ICDRT).
(2) In the I
bus line’s state after the issue of the stop-condition signal.
(3) Detection of the stop condition when the interface is in I
2
C bus format or the serial format, detection of the stop condition from the
2
C bus format.
(4) In the receive mode (TRS = 0) (writing of 0 to TRS during transmission is enabled
after reception of a frame that includes the acknowledge bit).
The next datum for transmission can be written to ICDR (ICDRT).
[Setting conditions]
1
(1) Detection, by the I
(TRS = 1), of the start condition from the bus line’s state after the issue of the
start-condition signal.
(2) Transfer of data from ICDRT to ICDRS (data is transferred from ICDRT to ICDRS
when TRS = 1, TDRE = 0, and ICDRS is empty).
(3) Changing of the mode from reception (TRS = 0) to transmission (TRS = 1) after
detection of the start condition.
2
C bus format or the serial format in the master mode
RDRF
Description
0
The datum in ICDR (ICDRR) is invalid.
[Clearing condition]
When, in the receive mode, data received in ICDR (ICDRR) is read.
(Initial Condition)
1
The data received in ICDR (ICDRR) can be read.
[Setting condition]
When data is transferred from ICDRS to ICDRR.
When the correct reception of data is allowed by TRS and RDRF both being 0, any
received data is transferred from ICDRS to ICDRR.