DS1821

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A status register is also present, indicating the status of the thermostatic control, and allowing

configuration of the output polarity as either active high or active low, and establishes the power-up state

of the device.

The status register is defined as follows:

where,

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

THF

= Temperature High Flag. This bit will normally be 0, but will be set to 1 when the temperature

exceeds the value of TH. It will remain 1 until reset by writing 0 into this location. This feature provides a

method of determining if the DS1821 has ever been subjected to temperatures above TH. This bit is

TLF

= Temperature Low Flag. This bit will normally be 0, but will be set to 1 when the temperature

is lower than the value of TL. It will remain 1 until reset by writing 0 into this location. This feature

provides a method of determining if the DS1821 has ever been subjected to temperatures below TL. This

NVB

T/R*

= Power-up mode bit. If set to a 1, the DS1821 will power up in a thermostat mode. If set to a

0, the device will power up in 1-Wire “read” mode. This bit is nonvolatile.

POL

= Output Polarity Bit. 1 = active high, 0 = active low. This bit is nonvolatile.

1SHOT = One-Shot Mode. If 1SHOT is 1, the DS1821 will perform one temperature conversion upon

reception of the Start Convert T protocol. If 1SHOT is 0, the DS1821 will continuously perform

temperature conversions. Note that the One-Shot mode is available only when the device is in 1-Wire

mode. In thermostat mode, the device continuously performs temperature conversions. This bit is

nonvolatile.

DONE

1

NVB

THF

TLF

T/R

POL

1SHOT