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Chapter 11 Inter-Integrated Circuit (S08IICV2)

MC9S08DZ128 Series Data Sheet, Rev. 1

Freescale Semiconductor

243

11.4

Functional Description

This section provides a complete functional description of the IIC module.

11.4.1

IIC Protocol

The IIC bus system uses a serial data line (SDA) and a serial clock line (SCL) for data transfer. All devices

connected to it must have open drain or open collector outputs. A logic AND function is exercised on both

lines with external pull-up resistors. The value of these resistors is system dependent.

Normally, a standard communication is composed of four parts:

•

Start signal

•

Slave address transmission

•

Data transfer

•

Stop signal

The stop signal should not be confused with the CPU stop instruction. The IIC bus system communication

is described brieﬂy in the following sections and illustrated in Figure 11-9.

Table 11-9. IICxC2 Field Descriptions

Field

Description

GCAEN

General Call Address Enable. The GCAEN bit enables or disables general call address.

0 General call address is disabled

1 General call address is enabled

ADEXT

Address Extension. The ADEXT bit controls the number of bits used for the slave address.

0 7-bit address scheme

1 10-bit address scheme

2–0

AD[10:8]

Slave Address. The AD[10:8] ﬁeld contains the upper three bits of the slave address in the 10-bit address

scheme. This ﬁeld is only valid when the ADEXT bit is set.

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