CHAPTER 17 SERIAL INTERFACE IIC0
Preliminary User’s Manual U17260EJ3V1UD
423
For example, the I
2
C transfer clock frequency (f
SCL
) when f
W
= f
PRS
/2 = 4.19 MHz, m = 86, t
R
= 200 ns, and t
F
=
50 ns is calculated using following expression.
f
SCL
= 1/(88
×
238.7 ns + 200 ns + 50 ns)
≅
48.1 kHz
m
×
T + t
R
+ t
F
m/2
×
T
m/2
×
T
t
F
t
R
SCL0
SCL0
inversion
SCL0
inversion
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
(f
W
)
Transfer Clock
(f
W
/m)
Settable Selection Clock
(f
W
) Range
Operation Mode
0 0 0 0
f
PRS
/2 f
W
/44
2.00 to 4.19 MHz
0 0 0 1
f
PRS
/2 f
W
/86
0 0 1 0
f
PRS
/4 f
W
/86
4.19 to 8.38 MHz
0 0 1 1
f
EXSCL0
f
W
/66 6.4
MHz
Normal mode
(SMC0 bit = 0)
0 1 0
×
f
PRS
/2 f
W
/24
0 1 1 0
f
PRS
/4 f
W
/24
4.00 to 8.38 MHz
0 1 1 1
f
EXSCL0
f
W
/18 6.4
MHz
High-speed mode
(SMC0 bit = 1)
1 0
×
×
Setting prohibited
1 1 0
×
f
PRS
/2 f
W
/12
1 1 1 0
f
PRS
/4 f
W
/12
4.00 to 4.19 MHz
High-speed mode
(SMC0 bit = 1)
1 1 1 1
Setting
prohibited
Caution Determine the transfer clock frequency of I
2
C 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
. f
PRS
:
Peripheral hardware clock frequency
3
. f
EXSCL0
: External clock frequency from EXSCL0 pin