the ALERT is cleared by responding to the alert

response address and the temperature fault condition

still exists, ALERT is reasserted after the next tempera-

ture-monitoring cycle. To clear ALERT while the tempera-

ture is above the trip threshold, write a new high limit that

is higher than the current temperature. The ALERT out-

put is open drain, allowing multiple devices to share a

common interrupt line.

Alert Response Address

The SMBus alert response interrupt pointer provides

quick fault identification for simple slave devices like

temperature sensors. Upon receiving an ALERT inter-

rupt signal, the host master can broadcast a Receive

Byte transmission to the alert response slave address

(0001 100). Following such a broadcast, any slave

device that generated an interrupt attempts to identify

itself by putting its own address on the bus.

The alert response can activate several different slave

If more than one slave attempts to respond, bus arbitra-

±1°C, SMBus-Compatible Remote/Local

Temperature Sensor with Overtemperature Alarm

8

_______________________________________________________________________________________

ADDRESS

POR STATEFUNCTION

00h

00h (0000 0000)

Read local temperature

01h

00h (0000 0000)

Read remote temperature

02h

N/A

Read status byte

03h

10h (0001 0000)

Read configuration byte

05h

46h (0100 0110) +70

°C

Read local high limit

07h

78h (0111 1000) +120

°C Read remote high limit

09h

N/A

Write configuration byte

0Bh

N/A

Write local high limit

0DhN/A

Write remote high limit

0Fh

N/A

Single shot

10h

0000 0000

Read remote extended

temperature

11h

0000 0000

Read internal extended

temperature

FEh4Dh (0100 1101)

Read manufacturer ID

Table 3. Command-Byte Assignments

BIT

NAME

POR STATE

FUNCTION

7 (MSB)

MASK1

0

A 1 masks off (disables) the

ALERT interrupts.

6

STOP/RUN

0

A 1 puts the MAX6642 into standby mode.

5

External only

0

A 1 disables local temperature measurements so that only

remote temperature is measured. The measurement rate

becomes 8Hz.

4

Fault

queue

1

0:

ALERT is set by a single fault. 1: Two consecutive faults

are required to set

ALERT.

3 to 0

—

0000

Reserved.

Table 4. Configuration-Byte Bit Assignments

BIT

NAME

POR STATE

FUNCTION

7 (MSB)

BUSY

0

A 1 indicates the MAX6642 is busy converting.

6

LHIGH

0

A 1 indicates an internal high-temperature fault. Clear

LHIGH with a POR or by reading the status byte.

5

—

0

Reserved.

4

RHIGH

0

A 1 indicates an external high-temperature fault. Clear

RHIGH with a POR or by reading the status byte.

3

—

0

Reserved.

2

OPEN

0

A 1 indicates a diode open condition. Clear OPEN with a

POR or by reading the status byte when the condition no

longer exists.

1 to 0

—

0

Reserved.

Table 5. Status-Byte Bit Assignments