MCP2221 datasheet(39/80 Pages) MICROCHIP

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DS20005292B-page 39

MCP2221

3.1.5

I2C™ WRITE DATA

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

I2C Slave device (the speed is specified by the

STATUS/SET Parameters command).

The command will have the following effects:

•The I2C engine will send the “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 follows next and the I2C engine

awaits for the acknowledge bit from the slave.

• If the requested length is more than 60 bytes,

subsequent user bytes will be sent 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.

3.1.5.1

Responses

TABLE 3-20:

COMMAND STRUCTURE(1)

Byte

Index

Value

Effect

00x90

I2C Write Data – 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 2)

4-63

User data to be sent to the selected I2C slave device

Note 1:

When the requested transfer length is more than 60 bytes, subsequent “I2C Write Data” commands will

transport the reminder of the user data (till the requested length).

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 3-21:

RESPONSE 1 STRUCTURE

Byte

Index

Value

Effect

00x90

I2C Write Data – 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

3-63

Don’t

care

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