STTS751 datasheet(12/36 Pages) STMICROELECTRONICS

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SMBus interface

STTS751

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Doc ID 16483 Rev 5

3.6

SMBus addresses

The STTS751 is available in two versions. Each version has 4 slave addresses determined

by the pull-up resistor value connected to the Addr/Therm pin. Refer to Table 1 for valid

address and recommended resistor values. The device will not respond to an invalid slave

address.

3.7

SMBus timeout

The STTS751 supports SMBus timeout which is enabled by default at power-up. This can

be disabled via bit 7 in the timeout register, refer to Section 4.11: SMBus timeout register.

When timeout is enabled, the STTS751 will time out after 25 to 35 ms of inactivity.

The STTS751 supports the SMBus timeout feature. If the host holds SCL low or the device

drives SDA low for more than tTIMEOUT (max), the STTS751 resets and releases the bus.

This feature is turned on by default. The STTS751 also supports timeout while in standby

mode and when the device is driving SDA low.

Note:

The STTS751 never drives the clock line and it does not support clock stretching.

3.8

Alert response address

The STTS751supports the SMBus alert response address (ARA) protocol. In the event of

an out-of-limit temperature measurement, the EVENT output will be asserted. In response,

the host (supporting the ARA protocol) will send the SMBus Alert Response Address to the

general (slave) address of 0001_100b. All devices with active interrupts will respond with

their client addresses as shown in Table1 on page1 (with the LSB bit set to 0).

The STTS751 will acknowledge the ARA and respond with its slave device address. Table 8

shows the ARA transfer. See Section 5 for more information.

Table 8.

SMBus protocol response to ARA

Field

START

ALERT

RESPONSE

ADDRESS

ACK

STTS751

SLAVE

ADDRESS

NACK

STOP

Bits

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