HCS08 datasheet(164/374 Pages) NXP

164 / 374 page

MC9S08JM60 Series Data Sheet, Rev. 5

164

Freescale Semiconductor

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 11-2. IICF Field Descriptions

Field

Description

7–6

MULT

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

5–0

ICR

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.

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

Eqn. 11-3

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).

SCL Stop hold time = bus period (s)

× mul × SCL Stop hold value

Eqn. 11-4

Table 11-3. Hold Time Values for 8 MHz Bus Speed

MULT

ICR

Hold Times (

μs)

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

IIC baud rate

bus speed (Hz)

mul

SCLdivider

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