LM83 datasheet(11/20 Pages) NSC

11 / 20 page

1.0 Functional Description (Continued)

1.9 COMMUNICATING with the LM83

There are 19 data registers in the LM83, selected by the

Command Register. At power-up the Command Register is

set to “00”, the location for the Read Local Temperature Reg-

ister. The Command Register latches the last location it was

set to. Reading the Status Register resets T_CRIT_A and

INT, so long as a temperature comparison does not signal a

fault (see

Sections 1.2 and 1.3). All other registers are pre-

defined as read only or write only. Read and write registers

with the same function contain mirrored data.

A Write to the LM83 will always include the address byte and

the command byte. A write to any register requires one data

byte.

Reading the LM83 can take place either of two ways:

If the location latched in the Command Register is cor-

rect (most of the time it is expected that the Command

isters because that will be the data most frequently read

from the LM83), then the read can simply consist of an

address byte, followed by retrieving the data byte.

If the Command Register needs to be set, then an ad-

dress byte, command byte, repeat start, and another ad-

dress byte will accomplish a read.

The data byte has the most significant bit first. At the end of

a read, the LM83 can accept either Acknowledge or No Ac-

knowledge from the Master (No Acknowledge is typically

used as a signal for the slave that the Master has read its

last byte).

1.10 SERIAL INTERFACE ERROR RECOVERY

The LM83 SMBus lines will be reset to the SMBus idle state

if the SMBData or SMBCLK lines are held low for 40 ms or

more (t

TIMEOUT). The LM83 may or may not reset the state of

DS101058-9

LM83 Datasheet(PDF) 11 Page - National Semiconductor (TI)