DS1720SSLASHT&R datasheet(6/14 Pages) MAXIM

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DS1720

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THERMOSTAT OUTPUT OPERATION Figure 3

OPERATION AND CONTROL

The DS1720 must have temperature settings resident in the TH and TL registers for thermostatic operation.

A configuration/status register is also used to determine the method of operation that the DS1720 will use

in a particular application, as well as indicating the status of the temperature conversion operation. The

configuration register is defined as follows:

CONFIGURATION/STATUS REGISTER

DONE

THF

TLF

NVB

CPU

1SHOT

where

DONE = Conversion Done bit. 1=conversion complete, 0=conversion in progress.

THF = Temperature High Flag. This bit will be set to 1 when the temperature is greater than or equal to

the value of TH. It will remain 1 until reset by writing 0 into this location or by removing power from the

device. This feature provides a method of determining if the DS1720 has ever been subjected to

temperatures above TH while power has been applied.

TLF = Temperature Low Flag. This bit will be set to 1 when the temperature is less than or equal to the

value of TL. It will remain 1 until reset by writing 0 into this location or by removing power from the

device. This feature provides a method of determining if the DS1720 has ever been subjected to

temperatures below TL while power has been applied.

NVB = Nonvolatile Memory Busy Flag. 1=write to an E

2 memory cell in progress. 0=nonvolatile

memory is not busy. A copy to E

2 may take up to 10 ms.

CPU = CPU use bit. If CPU=0, the CLK/ CONV pin acts as a conversion start control, when RST is low.

If CPU is 1, the DS1720 will be used with a CPU communicating to it over the 3–wire port, and the

operation of the CLK/ CONV pin is as a normal clock in concert with DQ and RST . This bit is stored in

nonvolatile E

2 memory, capable of at least 50,000 writes. The DS1720 is shipped with CPU=0.

1SHOT = One–Shot Mode. If 1SHOT is 1, the DS1720 will perform one temperature conversion upon

reception of the Start Convert T protocol. If 1SHOT is 0, the DS1720 will continuously perform

temperature conversion. This bit is stored in nonvolatile E 2 memory, capable of at least 50,000 writes.

The DS1720 is shipped with 1SHOT=0.

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