LM64 datasheet(11/29 Pages) NSC

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1.0 Functional Description (Continued)

Master sends a START followed by the Alert Response

Address (ARA) with a Read Command.

Alerting Device(s) send ACK.

Alerting Device(s) send their address. While transmitting

their address, alerting devices sense whether their ad-

dress has been transmitted correctly. (The LM64 will

reset its ALERT output and set the ALERT Mask bit once

its complete address has been transmitted successfully.)

Master/slave NoACK

Master sends STOP

Master attends to conditions that caused the ALERT to

be triggered. The ALERT Status Register is read and fan

started, setpoints adjusted, etc.

Master resets the ALERT Mask bit in the Configuration

The ARA, 000 1100, is a general call address. No device

should ever be assigned to this address.

The ALERT Configuration bit in the Remote Diode Tempera-

ture Filter and Comparator Mode Register must be set low in

order for the LM64 to respond to the ARA command.

The ALERT output can be disabled by setting the ALERT

Mask bit in the Configuration Register. The power-on default

is to have the ALERT Mask bit and the ALERT Configuration

bit low.

1.3 SMBus INTERFACE

Since the LM64 operates as a slave on the SMBus, the

SMBCLK line is an input and the SMBDAT line is bi-

directional. The LM64 never drives the SMBCLK line and it

does not support clock stretching. The LM64 has two

hardware-selectable 7-bit slave addresses. The user may

input a logical High or Low on the A0 Address pin to select

one of the two pre-programmed SMBus slave addresses.

The options are as follows:

SMBus

Address

0x[Hex]

SMBus Slave Address Bits

001100

100111

1.4 POWER-ON RESET (POR) DEFAULT STATES

For information on the POR default states see Section 2.2

LM64 Register Map in Functional Order.

20065509

FIGURE 6. ALERT Output as an SMBus ALERT

Temperature Response Diagram

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