MC9S08QE16CLC Datasheet, PDF (198/350 Pages) Freescale Semiconductor, Inc – Low-power wireless applications, Gas, water and heater meters

Inter-Integrated Circuit (S08IICV2)
Table 11-2. IICF Field Descriptions
Field
7–6
MULT
5–0
ICR
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 11-4 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 = ---b---u---s-----s---p---e----e---d-----(--H----z---)---
mul  SCLdivider
Eqn. 11-1
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. 11-2
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. 11-3
SCL Stop hold time = bus period (s)  mul  SCL Stop hold value
Eqn. 11-4
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 11-3. Hold Time Values for 8 MHz Bus Speed
MULT
0x2
0x1
0x1
0x0
0x0
ICR
0x00
0x07
0x0B
0x14
0x18
SDA
3.500
2.500
2.250
2.125
1.125
Hold Times (s)
SCL Start
SCL Stop
3.000
4.000
4.000
4.250
4.750
5.500
5.250
5.250
5.125
5.125
MC9S08AC60 Series Data Sheet, Rev. 3
198
Freescale Semiconductor