Datasheet

Section 15 I
2
C Bus Interface (IIC)
Rev. 3.00 Sep. 28, 2009 Page 355 of 710
REJ09B0384-0300
Bit Bit Name
Initial
Value
R/W Description
4 ICDRE 0 R Transmit Data Write Request Flag
Indicates the ICDR (ICDRT) status in transmit mode.
0: Indicates that the data has been already written to ICDR
(ICDRT) or ICDR is initialized.
1: Indicates that data has been transferred from ICDRT to
ICDRS and is being transmitted, or the start condition
has been detected or transmission has been complete,
thus allowing the next data to be written to.
[Setting conditions]
• When the start condition is detected from the bus line
state in I
2
C bus format or serial format.
• When data is transferred from ICDRT to ICDRS.
1. When data is transmitted completely while ICDRE
= 0 (at the rise of the 9th clock pulse).
2. When data is written to ICDR completely in transmit
mode after data was transmitted while ICDRE = 1.
[Clearing conditions]
• When data is written to ICDR (ICDRT).
• When the stop condition is detected in I
2
C bus format
or serial format.
• When 0 is written to the ICE bit.
Note that if the ACKE bit is set to 1 in I
2
C bus format thus
enabling acknowledge bit decision, ICDRE is not set when
data is transmitted completely while the acknowledge bit is
1.
When ICDRE is set due to the condition (2) above, ICDRE
is temporarily cleared to 0 when data is written to ICDR
(ICDRT); however, since data is transferred from ICDRT to
ICDRS immediately, ICDRF is set to 1 again. Do not write
data to ICDR when TRS = 0 because the ICDRE flag
value is invalid during the time.