DS1923 datasheet(21/52 Pages) DALLAS

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DS1923: Hygrochron Temperature/Humidity Logger iButton with 8kB Data Log Memory

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GENERAL STATUS

The information in the general status register tells the host computer whether a mission-related command was

executed successfully. Individual status bits indicate whether the DS1923 is performing a mission, waiting for a

temperature alarm to trigger the logging of data or whether the data from the latest mission has been cleared.

General Status Register Bitmap

ADDR

0215h

WFTA

MEMCLR

MIP

There is only read access to this register. Bits 0, 2, 5, 6, and 7 have no function.

Bit Description

Bit(s)

Definition

MIP: Mission In Progress

If this bit reads 1 the device has been set up for a mission and this

mission is still in progress. The MIP bit returns from logic 1 to logic 0

when a mission is ended. See function commands Start Mission and

Stop Mission.

MEMCLR: Memory

Cleared

If this bit reads 1, the Mission Time Stamp, Mission Sample Counter, as

well as all the alarm flags of the Alarm Status Register have been

cleared in preparation of a new mission. Executing the Clear Memory

command clears these memory sections. The MEMCLR bit returns to 0

as soon as a new mission is started by using the Start Mission

command. The memory has to be cleared in order for a mission to start.

WFTA: Waiting for

Temperature Alarm

If this bit reads 1, the Mission Start upon Temperature Alarm was

selected and the Start Mission command was successfully executed, but

the device has not yet experienced the temperature alarm. This bit is

cleared after a temperature alarm event, but is not affected by the Clear

Memory command. Once set, WFTA remains set if a mission is stopped

before a temperature alarm occurs. To clear WFTA manually before

starting a new mission, set the high temperature alarm (address 0209h)

to -40°C and perform a forced conversion.

MISSION START DELAY

The content of the Mission Start Delay Counter tells how many minutes have to expire from the time a mission was

started until the first measurement of the mission will take place (SUTA = 0) or until the device will start testing the

temperature for a temperature alarm (SUTA = 1). The Mission Start Delay is stored as an unsigned 24-bit integer

number. The maximum delay is 16777215 minutes, equivalent to 11650 days or roughly 31 years. If the start delay

is non-zero and the SUTA bit is set to 1, first the delay has to expire before the device starts testing for temperature

alarms to begin logging data.

Mission Start Delay Counter

ADDR

0216h

Delay Low Byte

0217h

Delay Center Byte

0218h

Delay High Byte

During a mission, there is only read access to these registers.

For a typical mission, the Mission Start Delay is 0. If a mission is too long for a single DS1923 to store all readings

at the selected sample rate, one can use several devices and set the Mission Start Delay for the second device to

start recording as soon as the memory of the first device is full, and so on. The RO bit in the Mission Control

DS1923 Datasheet(PDF) 21 Page - Dallas Semiconductor

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