DS2422 Maxim, DS2422 Datasheet - Page 15

• Manufacturer Part Number: DS2422
• Description: The DS2422 temperature/data logger combines the core functions of a fully featured data logger in a single chip
• Manufacturer: Maxim

The algorithm to convert the digital reading from the serial interface into a physical unit depends on the circuit that
provides the data to the DS2422. This algorithm needs to be reversed when calculating values for the alarm
threshold registers that are associated to the serial data input. The registers for data alarm thresholds are
located at address 020Ah (Low Alarm) and 020B (High Alarm). The comparison is based on the most
significant serial input byte and assumes that the data is represented as unsigned binary number.
TEMPERATURE SENSOR ALARM
The DS2422 has two Temperature Alarm Threshold registers (address 0208h, 0209h) to store values, which
determine whether a critical temperature has been reached. A temperature alarm is generated if the device
measures an alarming temperature AND the alarm signaling is enabled. The bits ETLA and ETHA that enable the
temperature alarm are located in the Temperature Sensor Control Register. The temperature alarm flags TLF and
THF are found in the Alarm Status Register at address 0214h.
Temperature Sensor Control Register Bitmap
During a mission, there is only read access to this register. Bits 2 to 7 have no function. They always read 0 and
cannot be written to 1.
Register Details
SERIAL INPUT ALARM
The DS2422 has two Data Alarm Threshold registers (address 020Ah, 020Bh) to store values, which determine
whether data read through the serial interface can generate an alarm. Such an alarm is generated if the input data
qualifies for an alarm AND the alarm signaling is enabled. The bits EDLA and EDHA that enable the serial input
alarm are located in the DATA_IF Control Register. The corresponding alarm flags DLF and DHF are found in the
Alarm Status Register at address 0214h.
DATA_IF Control Register Bitmap
During a mission, there is only read access to this register. Bits 3 to 7 have no function. They always read 1 and
cannot be written to 0.
ETLA: Enable Tempera-
ture Low Alarm
ETHA: Enable
Temperature High Alarm
ADDR
0210h
ADDR
0211h
BIT DESCRIPTION
b7
b7
0
1
b6
b6
0
1
BIT(S)
b5
b5
0
1
b0
b1
This bit controls whether, during a mission, the Temperature Low
Alarm Flag TLF may be set, if a temperature conversion results in a
value equal to or lower than the value in the Temperature Low Alarm
Threshold Register. If ETLA is 1, temperature low alarms are enabled.
If ETLA is 0, temperature low alarms are not generated.
This bit controls whether, during a mission, the Temperature High
Alarm Flag THF may be set, if a temperature conversion results in a
value equal to or higher than the value in the Temperature High Alarm
Threshold Register. If ETHA is 1, temperature high alarms are
enabled. If ETHA is 0, temperature high alarms are not generated.
b4
b4
0
1
15 of 49
b3
b3
0
1
b2
b2
0
1
EDHA
ETHA
DEFINITION
b1
b1
EDLA
ETLA
b0
b0