
R8C/3GM Group
25. I2C bus Interface
R01UH0284EJ0100 Rev.1.00
Aug 09, 2011
25.2.6
IIC bus Control Register 1 (ICCR1)
Notes:
1. Set according to the necessary transfer rate in master mode. Refer to Tables 25.4 and 25.5 Transfer Rate Examples
for the transfer rate. This bit is used for maintaining the setup time in transmit mode of slave mode.
The time is 10Tcyc when the CKS3 bit is set to 0 and 20Tcyc when the CKS3 bit is set to 1. (1Tcyc = 1/f1(s))
2. Rewrite the TRS bit between transfer frames.
3. When the first 7 bits after the start condition in slave receive mode match the slave address set in the SAR
register and the 8th bit is set to 1, the TRS bit is set to 1.
4. In master mode with the I2C bus format, if arbitration is lost, bits MST and TRS are set to 0 and the IIC enters
slave receive mode.
5. When an overrun error occurs in master receive mode with the clock synchronous serial format, the MST bit is
set to 0 and the I2C bus enters slave receive mode.
6. In multimaster operation, use the MOV instruction to set bits TRS and MST.
7. When writing 0 to the ICE bit or 1 to the IICRST bit in the ICCR2 register during an I2C bus interface operation,
the BBSY bit in the ICCR2 register and the STOP bit in the ICSR register may become undefined. Refer to 25.9 Address 0198h
Bit
b7b6b5
b4b3b2
b1b0
Symbol
After Reset
000
00
Bit
Symbol
Bit Name
Function
R/W
b0
CKS0
Transmit clock select bits 3 to 0
(1) b3 b2 b1 b0
0 0 0 0: f1/28
0 0 0 1: f1/40
0 0 1 0: f1/48
0 0 1 1: f1/64
0 1 0 0: f1/80
0 1 0 1: f1/100
0 1 1 0: f1/112
0 1 1 1: f1/128
1 0 0 0: f1/56
1 0 0 1: f1/80
1 0 1 0: f1/96
1 0 1 1: f1/128
1 1 0 0: f1/160
1 1 0 1: f1/200
1 1 1 0: f1/224
1 1 1 1: f1/256
R/W
b1
CKS1
R/W
b2
CKS2
R/W
b3
CKS3
R/W
b4
TRS
b5 b4
0 0: Slave Receive Mode
(4)0 1: Slave Transmit Mode
1 0: Master Receive Mode
1 1: Master Transmit Mode
R/W
b5
MST
Master/slave select bit
(5, 6)R/W
b6
RCVD
Receive disable bit
After reading the ICDRR register while the TRS bit is
set to 0
0: Next receive operation continues
1: Next receive operation disabled
R/W
b7
ICE
I2C bus interface enable bit (7) 0: This module is halted
(Pins SCL and SDA are set to a port function)
1: This module is enabled for transfer operations
(Pins SCL and SDA are in a bus drive state)
R/W