MCP2221 datasheet(43/80 Pages) MICROCHIP

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DS20005292B-page 43

MCP2221

3.1.9

I2C™ READ DATA

REPEATED-START

This command is used to read user-given data to the

I2C Slave device (the speed is specified by the

STATUS/SET Parameters command).

The command will have the following effect:

•The I2C engine will send the “Repeated-START”

condition.

• The selected I2C slave address is sent next and

the I2C engine will wait for the slave to send an

acknowledge bit.

• The user data is read next and the I2C engine

sends the acknowledge bit to the slave.

• If the requested length is more than 60 bytes,

subsequent user bytes will be read from the I2C

slave on the bus.

• When the user data length (being sent on the bus)

reaches the requested length, the I2C engine will

send the “STOP” condition on the bus.

3.1.9.1

Responses

TABLE 3-28:

COMMAND STRUCTURE

Byte

Index

Value

Effect

00x93

I2C Read Data Repeated-START – command code

Low Byte Requested I2C transfer length – 16-bit value – low byte

High Byte Requested I2C transfer length – 16-bit value – high byte

3I2C Slave

Address

8-bit value representing the I2C slave address to communicate with (even – address to write,

odd – address to read) (Note 1)

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Note 1:

The I2C slave address is represented on 8 bits, with even values for writes and odd for reads. To get the

8-bit address value out of a 7-bit address, the 7-bit value needs to be shifted left by 1 position. For write

operations use the shifted value, while for reads add 1 to the shifted value.

TABLE 3-29:

RESPONSE 1 STRUCTURE

Byte

Index

Value

Effect

0x93

I2C Read Data Repeated-START – command code echo

0x00

Command completed successfully

0x01

I2C Engine is busy (command not completed)

Internal I2C Engine state (at the moment the command was issued) – useful for monitoring the

status of the I2C Engine

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