RX610 Group
22. I
2
C Bus Interface (RIIC)
R01UH0032EJ0120 Rev.1.20
Page 723 of 1006
Feb 20, 2013
22.2.14 I
2
C Bus Bit Rate High-Level Register (ICBRH)
Addresses: RIIC0.ICBRL 0008 8311h, RIIC1.ICBRL 0008 8331h
b7
b6
b5
b4
b3
b2
b1
b0
Value after reset:
1
1
1
1
1
1
1
1
—
—
—
BRH[4:0]
Bit
Symbol
Bit Name
Description
R/W
b4 to b0
BRH[4:0]
Bit Rate High-Level Period
High-level period of SCL clock
R/W
b7 to b5
Reserved
These bits are always read as 1. The write value should always
be 1.
R/W
ICBRH is a 5-bit register to set the high-level period of SCL clock. ICBRH is valid in master mode. If the RIIC is used
only in slave mode, this register need not to set the high-level period.
ICBRH counts the high-level period with the internal reference clock source (IIC
φ
) specified by the CKS[2:0] bits in
ICMR1.
The I
2
C transfer rate and the SCL clock duty ratio are calculated using the following expression.
Transfer rate = 1 / { [(ICBRH + 1) + (ICBRL + 1)] / IIC
φ
*1 + SCLn line rising time [tr] + SCLn line falling time
[tf]}
Duty cycle = { SCLn line rising time [tr]*2 + (ICBRH + 1) / IIC
φ
} / {SCLn line falling time [tf]*2 + (ICBRL + 1) /
IIC
φ
}
Notes:
1. IIC
φ
= PCLK × 106 × Division ratio
2. The SCLn line rising time [tr] and SCLn line falling time [tf] depend on the total bus line capacitance [Cb]
and the pull-up resistor [Rp]. For details, see the I
2
C bus standard from NXP Semiconductors.