LM93 datasheet(22/92 Pages) NSC

22 / 92 page

14.0 SMBus Interface (Continued)

14.5.4 Read Operations

The LM93 uses the following SMBus read protocols.

14.5.4.1 Read Byte

In the LM93, the read byte protocol is used to read a single byte of data from a register. In this operation the master device

receives a single byte from a slave device, as follows:

The master device asserts a START condition.

The master sends the 7-bit slave address followed by the write bit (low).

The addressed slave device asserts ACK.

The master sends a register address.

The slave asserts an ACK.

The master sends a Repeated START.

The master sends the slave address followed by the read bit (high).

The slave asserts an ACK.

The master receives a data byte and asserts a NACK.

10. The master asserts a STOP condition and the transaction ends.

567

Slave

Address

Slave

Address

Data

Byte

14.5.4.2 Read Word

In the LM93, the read word protocol is used to read two bytes of data from a register or two consecutive registers. In this operation

the master device reads two bytes from a slave device, as follows:

The master device asserts a START condition.

The master sends the 7-bit slave address followed by the write bit (low).

The addressed slave device asserts ACK.

The master sends a register address.

The slave asserts an ACK.

The master sends a Repeated START.

The master sends the slave address followed by the read bit (high).

The slave asserts an ACK.

The master receives the Low data byte and asserts an ACK.

10. The master receives the High data byte and asserts a NACK.

11. The master asserts a STOP condition and the transaction ends.

567

Slave

Address

Slave

Address

Data

Byte Low

Data

Byte High

14.5.4.3 SMBus Block-Write Block-Read Process Call

This transaction is used to read a block of data from the LM93. Below is the sequence of events that occur in this transaction:

The master device asserts a START condition.

The master sends the 7-bit slave address followed by the write bit (low).

The addressed slave device asserts ACK.

The master sends a command code that tells the slave device to expect a block read (F1h) and the slave asserts ACK.

The master sends the Byte Count for this write which is 2 and the slave asserts ACK.

The master sends the Start Register Address for the block read and the slave asserts the ACK.

The master sends the Byte Count (1-32) for the block read processes call and the slave asserts ACK.

The master asserts a repeat START condition.

The master sends the 7-bit slave address followed by the read bit (high).

10. The slave asserts ACK.

11. The master receives a byte count data byte that tells it how many data bytes will received. This field reflects the number of

bytes requested by the Byte Count transmitted to the LM93. The SMBus specification allows a maximum of 32 data bytes to

be received in a block read. Then master asserts ACK.

LM93 데이터시트(PDF) 22 Page - National Semiconductor (TI)

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