RX610 Group
22. I
2
C Bus Interface (RIIC)
R01UH0032EJ0120 Rev.1.20
Page 753 of 1006
Feb 20, 2013
22.8
Function to Automatically Hold SCLn Clock Low
22.8.1
Function to Prevent Wrong Transmission of Transmit Data
If the shift register (ICDRS) is empty when data have not been written to the transmit data register (ICDRT) with the
RIIC in transmission mode (TRS bit = 1 in ICCR2), the SCLn signal is automatically held at the low level over the
intervals shown below. This low-hold period is extended until data for transmission have been written, which prevents
the unintended transmission of erroneous data.
<Master transmitter mode>
•
Low-level interval after a start condition or restart condition is issued
•
Low-level interval of one clock cycle between the ninth clock cycle of one transfer and the first clock cycle of the
next
<Slave transmitter mode>
•
Low-level interval between the ninth clock cycle of one transfer and the first clock cycle of the next
8
R
9
ACK
TDRE
AASn
TRS
BBSY
RDRF
S
1
2
3
4
5
6
7
2
3
4
5
6
7
8
9
ACK
2
3
[Master transmit mode]
[Slave transmit mode]
TDRE
AASn
TRS
BBSY
RDRF
S
2
3
4
5
6
7
2
3
4
5
6
7
8
9
ACK
8
W
9
ACK
2
SCLn
SDAn
SCLn
SDAn
1
1
1
1
1
Data (DATA1)
7-bit slave address
Data (DATA1)
7-bit slave address
Write data to ICDRT
(DATA1)
Write data to ICDRT
(DATA2)
Write data to ICDRT
(DATA2)
Write data to ICDRT
(DATA1)
Write data to ICDRT
(7-bit a W)
Transmit data (7-bit a W)
Transmit data (DATA1)
Transmit data (DATA2)
Transmit data (DATA1)
Address match
Automatic low-hold (to prevent wrong transmission)
Automatic low-hold
(to prevent wrong
transmission)
Automatic low-hold
(to prevent wrong
transmission)
Automatic low-hold (to prevent wrong transmission)
Automatic low-hold (to prevent wrong transmission)
Transmit data (DATA2)
Figure 22.29 Automatic Low-Hold Operation in Transmit Mode