ST72734 datasheet(95/144 Pages) STMICROELECTRONICS

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ST72774/ST727754/ST72734

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4.8 DDC INTERFACE (DDC)

4.8.1 Introduction

The DDC (Display Data Channel) Bus Interface is

mainly used by the monitor to identify itself to the

video controller, by the monitor manufacturer to

perform factory alignment, and by the user to

adjust the monitor’s parameters.

The DDC interface consists of two parts:

fully

hardware-implemented

interface,

supporting

DDC1

and

DDC2B

(VESA

specification 3.0 compliant). It accesses the

ST7 on-chip memory directly through a built-in

DMA engine.

A second interface, supporting the slave I2C

functions for handling DDC/CI mode (DDC2Bi),

factory alignment or Enhanced DDC (EDDC) by

software.

4.8.2 DDC Interface Features

4.8.2.1 Hardware DDC1/2B Interface Features

Full

hardware

support

for

DDC1/2B

communications (VESA specification versions 2

and 3)

Hardware detection of DDC2B addresses A0h/

A1h and optionally A2h/A3h (P&D) or A6h/A7h

(FPDI-2)

Separate mapping of EDID version 1 (128

bytes) and EDID version 2 (256 bytes) when

both must coexist

Support for error recovery mechanism

Detection

misplaced

Start

and

Stop

conditions

I2C byte, random and sequential read modes

DMA transfer from any memory location and to

RAM

Automatic memory address incrementation

End of data downloading flag and interrupt

capability

4.8.2.2 DDC/CI - Factory Interface Features

General I2C Features:

– Parallel bus /I2C protocol converter

– Interrupt generation

– Standard I2C mode/Fast I2C mode

– 7-bit Addressing

I2C Slave Features:

–I2C bus busy flag

– Start bit detection flag

– Detection of misplaced Start or Stop condition

– Transfer problem detection

– Address Matched detection

– Programmable

Address

detection

and/or

Hardware detection of Enhanced DDC (ED-

DC) addresses (60h/61h)

– End of byte transmission flag

– Transmitter/Receiver flag

– Stop condition Detection

Figure 56. DDC Interface Overview

SDAD

SCLD

VSYNCI

SDA

SCL

VSYNC

HARDWARE DDC1/2B

INTERFACE

I2C SLAVE

INTERFACE

(DDC/CI - Factory Alignment)

VSYNCI2

VSYNC2

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