DS9101 datasheet(22/55 Pages) MAXIM

22 / 55 page

Hygrochron Temperature/Humidity Logger

iButton with 8KB Data-Log Memory

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Alarm Status

The fastest way to determine whether a programmed

temperature or humidity threshold was exceeded during

a mission is through reading the Alarm Status register.

In a networked environment that contains multiple

DS1923 iButtons, the devices that encountered an alarm

can quickly be identified by means of the Conditional

Search ROM command (see the

1-Wire ROM Function

Commands section). The humidity and temperature

alarm only occurs if enabled (see the

Temperature

Sensor Alarm and Humidity Alarm sections). The BOR

alarm is always enabled.

Bit 7: Battery-On Reset Alarm (BOR). If this bit reads

1, the device has performed a power-on reset. This

indicates that the device has experienced a shock big

enough to interrupt the internal battery power supply.

The device can still appear functional, but it has lost its

factory calibration. Any data found in the data-log

memory should be disregarded.

Bit 3: Humidity High Alarm Flag (HHF). If this bit

reads 1, there was at least one humidity reading during

a mission revealing a value equal to or higher than the

value in the Humidity High Alarm register. A forced

conversion can affect the HHF bit.

Bit 2: Humidity Low Alarm Flag (HLF). If this bit reads

1, there was at least one humidity reading during a mis-

sion revealing a value equal to or lower than the value

in the Humidity Low Alarm register. A forced conversion

can affect the HLF bit.

Bit 1: Temperature High Alarm Flag (THF). If this bit

reads 1, there was at least one temperature conversion

during a mission revealing a temperature equal to or

higher than the value in the Temperature High Alarm

This bit can also be set with the initial alarm in the

SUTA = 1 mode.

Bit 0: Temperature Low Alarm Flag (TLF). If this bit

reads 1, there was at least one temperature conversion

during a mission revealing a temperature equal to or

lower than the value in the Temperature Low Alarm reg-

ister. A forced conversion can affect the TLF bit. This

bit can also be set with the initial alarm in the SUTA = 1

mode.

General Status

The information in the General Status register tells the

host computer whether a mission-related command

was executed successfully. Individual status bits indi-

cate whether the DS1923 is performing a mission, wait-

ing for a temperature alarm to trigger the logging of

data or whether the data from the latest mission has

been cleared.

Bit 4: Waiting for Temperature Alarm (WFTA). If this

bit reads 1, the mission start upon temperature alarm

was selected and the Start Mission command was suc-

cessfully executed, but the device has not yet experi-

enced 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.

Bit 3: Memory Cleared (MEMCLR). If this bit reads 1,

the Mission Timestamp, Mission Samples Counter, and

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 sec-

tions. The MEMCLR bit returns to 0 as soon as a new

mission is started by using the Start Mission command.

The memory must be cleared for a mission to start.

Bit 1: Mission in Progress (MIP). 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 the

Start Mission [with

Password] [CCh] and Stop Mission [with Password]

[33h] sections.

Alarm Status Register Bitmap

ADDRESS

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

0214h

BOR

HHF

HLF

THF

TLF

General Status Register Bitmap

ADDRESS

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

0215h

WFTA

MEMCLR

MIP

Note: There is only read access to this register. Bits 4 to 6 have no function. They always read 1. All five alarm status bits are cleared

simultaneously when the Clear Memory command is invoked. See the Memory and Control Function Commands section for details.

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

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