![](http://datasheet.mmic.net.cn/390000/LM64_datasheet_16816027/LM64_11.png)
1.0 Functional Description
(Continued)
2.
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 theALERT 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. TheALERT Status Register is read and fan
started, setpoints adjusted, etc.
Master resets the ALERT Mask bit in the Configuration
Register.
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.
3.
4.
5.
6.
7.
8.
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:
A0
Pin
SMBus
Address
0x[Hex]
18
4E
SMBus Slave Address Bits
A6
A5
A4
A3
A2
A1
A0
0
1
0
1
0
0
1
0
1
1
0
1
0
1
0
0
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
L
www.national.com
11