Freescale Semiconductor MCF51QE128RM manual IIC Protocol, IICC2 Field Descriptions, Gcaen

Models: MCF51QE128RM

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Table 13-9. IICC2 Field Descriptions

 

 

 

Field

 

Description

 

 

7

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

GCAEN

0

General call address is disabled

 

1

General call address is enabled

 

 

6

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

ADEXT

0

7-bit address scheme

 

1

10-bit address scheme

 

 

2–0

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

AD[10:8]

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

 

 

 

13.4Functional Description

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

13.4.1IIC 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 13-9.

MCF51QE128 MCU Series Reference Manual, Rev. 3

2-270

Freescale Semiconductor

Page 270
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Freescale Semiconductor MCF51QE128RM manual IIC Protocol, IICC2 Field Descriptions, Gcaen