590
Chapter 18
I
2
C Bus (IIC)
Preliminary User’s Manual U17566EE1V2UM00
(7)
Transfer rate setting
The nominal transfer rate of the I
2
C interface is determined by the following
means:
• the root clock source for the I
2
C clock IICLK can be chosen as
– main oscillator (4 MHz): ICC.IICSEL1 = 0
– 32 MHz clock from the PLL: ICC.IICSEL1 = 1
The output clock IICLK supplies the IIC interface.
• The IICLK is divided by 1 to 5, configured by OCKSn.OCKSTHn and
OCKSn.OCKSTn[1:0] (refer to
“OCKSn - IICn division clock select registers“
on page 589
). The output clock of this divider is named IICLKPS.
• IICLKPS is passed through another configurable divider that finally outputs
the clock for the serial transfer IICLKTC. This divider is configured by
IICCLn.CL[1:0] and IICXn.CLX0 according to the following table:
Note
The clock chosen as the input clock, that means IICLKPS, must lie in the range
of 1 MHz to 10 MHz.
Following table lists set-ups for some useful I
2
C transfer clocks.
Note
The calculations in the above table assumes that IICLK is 32 MHz
(IIC.IICSEL1 = 1)
IICXn.CLXn
IICCLn.SMCn
IICCLn.CLn1
IICCLn.CLn0
Input clock
Transfer
clock
Mode
0
0
0
0
f
IICLKPS
f
IICLKPS
/44
standard
0
1
f
IICLKPS
f
IICLKPS
/86
standard
1
0
n.a.
n.a.
n.a.
1
1
f
IICLKPS
f
IICLKPS
/66
standard
1
0
0
f
IICLKPS
f
IICLKPS
/24
fast-speed
0
1
f
IICLKPS
f
IICLKPS
/24
fast-speed
1
0
n.a.
n.a.
n.a.
1
1
f
IICLKPS
f
IICLKPS
/18
fast-speed
1
0
x
x
n.a.
n.a.
n.a.
1
0
0
f
IICLKPS
f
IICLKPS
/12
fast-speed
0
1
f
IICLKPS
f
IICLKPS
/12
fast-speed
1
0
n.a.
n.a.
n.a.
1
1
f
IICLKPS
f
IICLKPS
/18
fast-speed
Prescaler
I
2
C module set-up
Transfer
clock
[KHz]
OCKSn
divisor
IICCLn.
SMCn
IICXn.
CLXn
IICCLn.
CLn[1:0]
divisor
1 0011
B
=
13
H
5
1
1
11
B
18
355,56
0
0
11
B
66
96,97
electronic components distributor