MC9S08SH32CWL Datasheet, PDF (154/328 Pages) Freescale Semiconductor, Inc – MC9S08SH32 Series Features

Chapter 10 Inter-Integrated Circuit (S08IICV2)
Field
7–6
MULT
5–0
ICR
Table 10-3. IICF Field Descriptions
Description
IIC Multiplier Factor. The MULT bits define the multiplier factor, mul. This factor, along with the SCL divider,
generates the IIC baud rate. The multiplier factor mul as defined by the MULT bits is provided below.
00 mul = 01
01 mul = 02
10 mul = 04
11 Reserved
IIC Clock Rate. The ICR bits are used to prescale the bus clock for bit rate selection. These bits and the MULT
bits determine the IIC baud rate, the SDA hold time, the SCL Start hold time, and the SCL Stop hold time.
Table 10-5 provides the SCL divider and hold values for corresponding values of the ICR.
The SCL divider multiplied by multiplier factor mul generates IIC baud rate.
IIC baud rate = _{m---b---uu---ls---×}--s--S-p---C-e---e-L--d-d---i-(-v-H--i-d--z--e-)--r
Eqn. 10-1
SDA hold time is the delay from the falling edge of SCL (IIC clock) to the changing of SDA (IIC data).
SDA hold time = bus period (s) × mul × SDA hold value
Eqn. 10-2
SCL start hold time is the delay from the falling edge of SDA (IIC data) while SCL is high (Start condition) to the
falling edge of SCL (IIC clock).
SCL Start hold time = bus period (s) × mul × SCL Start hold value
SCL stop hold time is the delay from the rising edge of SCL (IIC clock) to the rising edge of SDA
SDA (IIC data) while SCL is high (Stop condition).
Eqn. 10-3
SCL Stop hold time = bus period (s) × mul × SCL Stop hold value
Eqn. 10-4
For example, if the bus speed is 8 MHz, the table below shows the possible hold time values with different
ICR and MULT selections to achieve an IIC baud rate of 100kbps.
Table 10-4. Hold Time Values for 8 MHz Bus Speed
Hold Times (μs)
MULT
ICR
SDA
SCL Start
SCL Stop
0x2
0x00
3.500
3.000
5.500
0x1
0x07
2.500
4.000
5.250
0x1
0x0B
2.250
4.000
5.250
0x0
0x14
2.125
4.250
5.125
0x0
0x18
1.125
4.750
5.125
MC9S08SH32 Series Data Sheet, Rev. 2
154
Freescale Semiconductor
PRELIMINARY