Datasheet

I2C_F field descriptions
Field Description
7–6
MULT
The MULT bits define the multiplier factor mul. This factor is used along with the SCL divider to generate
the I2C baud rate.
00 mul = 1
01 mul = 2
10 mul = 4
11 Reserved
5–0
ICR
ClockRate
Prescales the bus clock for bit rate selection. This field and the MULT field determine the I2C baud rate,
the SDA hold time, the SCL start hold time, and the SCL stop hold time. For a list of values corresponding
to each ICR setting, see I2C divider and hold values.
The SCL divider multiplied by multiplier factor (mul) determines the I2C baud rate.
I2C baud rate = bus speed (Hz)/(mul × SCL divider)
The SDA hold time is the delay from the falling edge of SCL (I2C clock) to the changing of SDA (I2C data).
SDA hold time = bus period (s) × mul × SDA hold value
The SCL start hold time is the delay from the falling edge of SDA (I2C data) while SCL is high (start
condition) to the falling edge of SCL (I2C clock).
SCL start hold time = bus period (s) × mul × SCL start hold value
The SCL stop hold time is the delay from the rising edge of SCL (I2C clock) to the rising edge of SDA (I2C
data) while SCL is high (stop condition).
SCL stop hold time = bus period (s) × mul × SCL stop hold value
For example, if the bus speed is 8 MHz, the following table shows the possible hold time values with
different ICR and MULT selections to achieve an I
2
C baud rate of 100 kbps.
MULT ICR
Hold times (μs)
SDA SCL Start SCL Stop
2h 00h 3.500 3.000 5.500
1h 07h 2.500 4.000 5.250
1h 0Bh 2.250 4.000 5.250
0h 14h 2.125 4.250 5.125
0h 18h 1.125 4.750 5.125
Chapter 18 Inter-Integrated Circuit (I2C)
MC9S08PA60 Reference Manual, Rev. 1, 9/2012
Freescale Semiconductor, Inc. 497