1.6 COMMUNICATING with the LM73

The data registers in the LM73 are selected by the Pointer

Register. At power-up the Pointer Register is set to “00h”, the

location for the Temperature Register. The Pointer Register

latches the last location it was set to. Note that all Pointer

Register bits are decoded; any incorrect pointer values will

not be acknowledged and will not be stored in the Pointer

Register (Note 13).

A Write to the LM73 will always include the address byte and

the pointer byte.

A Read from the LM73 can take place either of two ways:

1.

If the location latched in the Pointer Register is correct

(that is, the Pointer Register is pre-set prior to the read),

then the read can simply consist of an address byte,

followed by retrieving the data byte. Most of the time it is

expected that the Pointer Register will point to Tempera-

ture Registers because that will be the data most fre-

quently read from the LM73.

2.

If the Pointer Register needs to be set, then an address

byte, pointer byte, repeat start, and another address

byte will accomplish a read.

The data byte is read out of the LM73 by the most significant

bit first. At the end of a read, the LM73 can accept either an

Acknowledge or No Acknowledge bit from the Master. No

Acknowledge is typically used as a signal to the slave that

the Master has read its last byte.

20147816

FIGURE 1. ALERT Temperature Response cleared

when temperature crosses T

LOW

20147817

FIGURE 2. ALERT Temperature Response cleared by

writing a "1" to the ALERT Reset Bit.

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