TIME

(Active Low)

Measured Temperature

ALERT 5HVHW %LW VHW WR ³1´

One

Conversion Time

ALERT

TIME

Measured Temperature

ALERT pin

LM73

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SNIS141F – OCTOBER 2005 – REVISED OCTOBER 2015

Figure 7. ALERT Temperature Response Cleared by Writing a 1 to the ALERT Reset Bit.

7.3.6 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

A write to an invalid pointer address is not allowed. If the master writes an invalid address

to the Pointer Register, the LM73 will not acknowledge the address and the Pointer

Register will continue to contain the last value stored in it.

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

A Read from the LM73 can occur in either of the following ways:

•

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 Temperature Registers because that will be the data

most frequently read from the LM73.

•

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.

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