Datasheet

DS1922L/DS1922T
Temperature Logger iButton with 8KB
Data-Log Memory
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Alarm Status
The fastest way to determine whether a programmed
temperature threshold was exceeded during a mission
is by reading the Alarm Status register. In a networked
environment that contains multiple DS1922L/
DS1922T i
Buttons, the devices that encountered an
alarm can quickly be identified by means of the
Conditional Search command (see the
1-Wire ROM
Function Commands section). The temperature alarm
only occurs if enabled (see the Temperature Sensor
Alarm section). 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 mem-
ory should be disregarded.
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
register. A forced conversion can affect the THF bit.
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 DS1922L/DS1922T are performing a
mission, waiting for a temperature alarm to trigger the
logging of data, or whether the data from the latest mis-
sion 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 sections. 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 and Stop Mission with Password sections.
Alarm Status Register Bitmap
ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
0214h BOR 1 1 1 0 0 THF TLF
General Status Register Bitmap
ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
0215h 1 1 0 WFTA MEMCLR 0 MIP 0
Note: There is only read access to this register. Bits 4 to 6 have no function. They always read 1. Bits 2 and 3 have no function with
the DS1922L/DS1922T. They always read 0. The alarm status bits are cleared simultaneously when the Clear Memory Function 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.