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CHAPTER 17 SERIAL INTERFACE IIC0
User’s Manual U17473EJ2V0UD
411
For example, the I
2C transfer clock frequency (fSCL) when fW = fPRS/2 = 4.19 MHz, m = 86, tR = 200 ns, and tF =
50 ns is calculated using following expression.
fSCL = 1/(88
× 238.7 ns + 200 ns + 50 ns) 48.1 kHz
m
× T + tR + tF
m/2
× T
m/2
× T
tF
tR
SCL0
SCL0 inversion
The selection clock is set using a combination of bits 3, 1, and 0 (SMC0, CL01, and CL00) of IIC clock selection
register 0 (IICCL0) and bit 0 (CLX0) of IIC function expansion register 0 (IICX0).
Table 17-2. Selection Clock Setting
IICX0
IICCL0
Bit 0
Bit 3
Bit 1
Bit 0
CLX0
SMC0
CL01
CL00
Selection Clock
(fW)
Transfer Clock
(fW/m)
Settable Selection Clock
(fW) Range
Operation Mode
0
fPRS/2
fW/44
2.00 to 4.19 MHz
0
1
fPRS/2
fW/86
0
1
0
fPRS/4
fW/86
4.19 to 8.38 MHz
Normal mode
(SMC0 bit = 0)
0
1
Setting prohibited
0
1
0
×
fPRS/2
fW/24
0
1
0
fPRS/4
fW/24
4.00 to 8.38 MHz
High-speed mode
(SMC0 bit = 1)
0
1
0
×
Setting prohibited
1
0
×
fPRS/2
fW/12
1
0
fPRS/4
fW/12
4.00 to 4.19 MHz
High-speed mode
(SMC0 bit = 1)
1
Setting prohibited
Caution
Determine the transfer clock frequency of I
2C by using CLX0, SMC0, CL01, and CL00 before
enabling the operation (by setting bit 7 (IICE0) of IIC control register 0 (IICC0) to 1). To change
the transfer clock frequency, clear IICE0 once to 0.
Remarks 1.
×:
don’t care
2. fPRS:
Peripheral hardware clock frequency
3. fEXSCL0:
External clock frequency from EXSCL0 pin