DS1821S+TR DALLAS [Dallas Semiconductor], DS1821S+TR Datasheet - Page 6

• Manufacturer Part Number: DS1821S+TR
• Description: Programmable Digital Thermostat and Thermometer
• Manufacturer: DALLAS [Dallas Semiconductor]

TEMPERATURE/DATA RELATIONSHIP Table 2
HIGH-RESOLUTION TEMPERATURE READINGS
The user can calculate temperature values with higher than 8-bit resolution using the data remaining in
the counter and slope accumulator when the temperature conversion is complete. To do this the user must
first read the temperature from the 8-bit temperature register. This value is called TEMP_READ in the
high-resolution equation (see Eq. 1). The 9-bit counter value must then be obtained by issuing the Read
Counter [A0h] command. This value is the count remaining in the counter at the end of the gate period
and is called COUNT_REMAIN in Eq. 1. Next the Load Counter [41h] command must be issued, which
loads the 9-bit slope accumulator value into the counter register. The slope accumulator value (called
COUNT_PER_C in Eq. 1) can then be read from the counter by again issuing the Read Counter [A0h]
command. The slope accumulator value is called “COUNT_PER_C” because it represents the number of
counts needed for an accurate measurement at a given temperature (i.e., the counts per degree C). The
high-resolution temperature can then be calculated using Eq. 1:
Eq. 1)
High-resolution temperature readings cannot be used while in continuous conversion mode. Also, the
Read Counter [A0h] and Load Counter [41h] commands must not be used while in continuous conversion
mode.
TEMPERATURE = TEMP_READ
TEMPERATURE
+125°C*
+85°C
+25°C
-25°C
-55°C
-1°C
0°C
DIGITAL OUTPUT
0111 1101
0101 0101
0001 1001
0000 0000
1111 1111
1110 0111
1100 1001
(Binary)
−
6 of 18
0.5
+
(
COUNT
DIGITAL OUTPUT
_
PER
COUNT
_
(Hex)
7Dh
FFh
E7h
C9h
55h
19h
00h
C
−
_
COUNT
PER
_
C
_
REMAIN
)