Rainbow Electronics DS1920 User Manual
Page 5
DS1920
5 of 22
The most significant (sign) bit is duplicated into all of the bits in the upper MSB of the 2-byte
temperature register in memory. This “sign-extension” yields the 16-bit temperature readings as shown in
Table 1.
Higher resolutions may be obtained by the following procedure. First, read the temperature, and truncate
the 0.5°C bit (the LSB) from the read value. This value is TEMP_READ. The value left in the counter
may then be read. This value is the count remaining (COUNT_REMAIN) after the gate period has
ceased. The last value needed is the number of counts per degree C (COUNT_PER_C) at that
temperature. The actual temperature may be then be calculated by the user using the following formula:
TEMPERATURE = TEMP_READ - 0.25 +
C
COUNT_PER_
IN)
COUNT_REMA
-
_C
(COUNT_PER
TEMPERATURE MEASURING CIRCUITRY Figure 3
TEMPERATURE/DATA RELATIONSHIPS Table 1
TEMPERATURE
DIGITAL OUTPUT
(BINARY)
DIGITAL OUTPUT
(HEX)
+100
°
C
00000000 11001000
00C8H
+25
°
C
00000000 00110010
0032H
+½
°
C
00000000 00000001
0001H
+0
°
C
00000000 00000000
0000H
-½
°
C
11111111 11111111
FFFFH
-25
°
C
11111111 11001110
FFCEH
-55
°
C
11111111 10010010
FF92H
SET/CLEAR
LSB