MCP47CMB21 datasheet(109/124 Pages) MICROCHIP

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DS20006089B-page 109

MCP47CXBXX

APPENDIX B: I2C SERIAL

INTERFACE

This I2C is a two-wire interface that allows multiple

devices to be connected to the two-wire bus. Figure B-1

shows a typical I2C interface connection.

FIGURE B-1:

Typical I2C Interface.

B.1

Overview

A device that sends data onto the bus is defined as a

transmitter and a device receiving data is defined as a

receiver. The bus has to be controlled by a Master

device which generates the Serial Clock (SCL), con-

trols the bus access and generates the Start and Stop

conditions. Devices that do not generate a serial clock

work as Slave devices. Both Master and Slave can

operate as transmitter or receiver, but the Master

device determines which mode is activated. Communi-

cation is initiated by the Master (microcontroller), which

sends the Start bit followed by the Slave address byte.

The first byte transmitted is always the Slave address

byte, which contains the device code, the address bits

and the R/W bit.

The I2C interface specifies different communication bit

rates. These are referred to as Standard, Fast or High-

Speed modes and the MCP47CXBXX supports these

three modes. The clock rates (bit rate) of these modes

are:

• Standard mode: Up to 100 kHz (kbit/s)

• Fast mode: Up to 400 kHz (kbit/s)

• High-Speed mode (HS mode): Up to 3.4 MHz

(Mbit/s)

The I2C protocol supports two addressing modes:

• 7-Bit Slave Addressing

• 10-Bit Slave Addressing (allows more devices on

the I2C bus)

Only 7-Bit Slave Addressing will be discussed in this

section.

The I2C serial protocol allows multiple Master devices

on the I2C bus. This is referred to as “Multi-Master”. For

this, all Master devices must support Multi-Master

operation. In this configuration, all Master devices mon-

itor their communication. If they detect that they wish to

transmit a bit that is a logic high, but is detected as a

logic low (some other Master device driving), they “get

off” the bus. That is, they stop their communication and

continue to listen to determine if the communication is

directed towards them.

The I2C serial protocol only defines the field types, field

lengths, timings, etc., of a frame. The frame content

defines the behavior of the device. For details on the

frame content (commands/data), refer to Section 7.0,

Device Commands.

The I2C serial protocol defines some commands, called

“General Call Addressing”, which allow the Master

device to communicate to all Slave devices on the I2C

bus.

SCL

Slave

SDA

Master

Typical I2C Interface Connections

Other Devices

Note:

Refer

the

“NXP

Specification

#UM10204”, Rev. 06, 4 April 2014

document for more details on the

I2C specifications.

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