UCS81003 datasheet(98/108 Pages) MICROCHIP

98 / 108 page

UCS81003

DS20005334A-page 98

 2014 Microchip Technology Inc.

11.2.3

SMBUS PROTOCOLS

The UCS81003 is SMBus 2.0-compatible and supports

Write Byte, Read Byte, Send Byte, and Receive Byte

as valid protocols as shown in the following sections.

All protocols in these sections use the convention in

Table 11-3.

11.2.3.1

SMBus Write Byte

The Write Byte is used to write one byte of data to a

specific register as shown in Table 11-4.

11.2.3.2

SMBus Read Byte

The Read Byte protocol is used to read one byte of data

from the registers as shown in Table 11-5.

11.2.3.3

SMBus Send Byte

The Send Byte protocol is used to set the internal

address register pointer to the correct address location.

No data is transferred during the Send Byte protocol as

shown in Table 11-6.

11.2.3.4

SMBus Receive Byte

The Receive Byte protocol is used to read data from a

known to be at the right location (e.g., set via Send

Byte). This is used for consecutive reads of the same

TABLE 11-3:

PROTOCOL FORMAT

Data Sent to Device

Data Sent to the Host

Data sent

TABLE 11-4:

WRITE BYTE PROTOCOL

START

Client

Address

ACK

Address

ACK

Data

ACK

STOP

1 ->0

YYYY_YYY

XXh

0 -> 1

TABLE 11-5:

READ BYTE PROTOCOL

START

Client

Address

ACK

Address

ACK

START

Client

Address

ACK

Data

NACK

STOP

1->0

YYYY_YYY

XXh

1 ->0

YYYY_YY

XXh

0 -> 1

TABLE 11-6:

SEND BYTE PROTOCOL

START

Client Address

ACK

Address

ACK

STOP

1 -> 0

YYYY_YYY

XXh

0 -> 1

TABLE 11-7:

RECEIVE BYTE PROTOCOL

START

CLIENT

ADDRESS

ACK

NACK

STOP

1 -> 0

YYYY_YYY

XXh

0 -> 1

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