1.12 FAULT QUEUE

In order to suppress erroneous ALERT or T_CRIT triggering

the LM89 incorporates a Fault Queue. The Fault Queue acts

to insure a remote temperature measurement is genuinely

beyond a HIGH, LOW or T_CRIT setpoint by not triggering

until three consecutive out of limit measurements have been

made, see Figure 10. The fault queue defaults off upon

power-up and may be activated by setting bit D0 in the

Configuration register (09h) to “1”.

1.13 ONE-SHOT REGISTER

The One-Shot register is used to initiate a single conversion

and comparison cycle when the device is in standby mode,

after which the device returns to standby. This is not a data

register and it is the write operation that causes the one-shot

conversion. The data written to this address is irrelevant and

is not stored. A zero will always be read from this register.

2.0 LM89 Registers

2.1 COMMAND REGISTER

Selects which registers will be read from or written to. Data for this register should be transmitted during the Command Byte of

the SMBus write communication.

P7

P6

P5

P4

P3

P2

P1

P0

Command Select

P0-P7: Command Select

Command Select Address

Power-On-Default State

Register

Name

Register Function

Read Address

Write Address

decimal

00h

NA

0000 0000

0

LT

Local Temperature

01h

NA

0000 0000

0

RTHB

Remote Temperature High Byte

02h

NA

0000 0000

0

SR

Status Register

03h

09h

0000 0000

0

C

Configuration

04h

0Ah

0000 1000

8 (16

conv./sec)

CR

Conversion Rate

05h

0Bh

0100 0110

70

LHS

Local HIGH Setpoint

06h

0Ch

0000 0000

0

LLS

Local LOW Setpoint

07h

0Dh

0100 0110

70

RHSHB

Remote HIGH Setpoint High Byte

08h

0Eh

0000 0000

0

RLSHB

Remote LOW Setpoint High Byte

NA

0Fh

One Shot

Writing to this register will initiate a

one shot conversion

10h

NA

0000 0000

0

RTLB

Remote Temperature Low Byte

11h

11h

0000 0000

0

RTOHB

Remote Temperature Offset High

Byte

20041530

FIGURE 10. Fault Queue Temperature Response

Diagram

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