Rainbow Electronics DS1621 User Manual
Page 4
DS1621
4 of 16
102299
TEMPERATURE MEASURING CIRCUITRY Figure 2
TEMPERATURE/DATA RELATIONSHIPS Table 2
TEMPERATURE
DIGITAL OUTPUT
(Binary)
DIGITAL OUTPUT
(Hex)
+125°C
01111101 00000000
7B00h
+25°C
00011001 00000000
1900h
+½°C
00000001 00000000
0080h
+0°C
00000000 00000000
0000h
-½°C
11111111 10000000
FF80h
-25°C
11100111 00000000
E700h
-55°C
11001001 00000000
C900h
Since data is transmitted over the 2–wire bus MSB first, temperature data may be written to/read from the
DS1621 as either a single byte (with temperature resolution of 1
°
C) or as two bytes. The second byte
would contain the value of the least significant (0.5
°
C) bit of the temperature reading as shown in Table
1. Note that the remaining 7 bits of this byte are set to all "0"s.
Temperature is represented in the DS1621 in terms of a ½
°
C LSB, yielding the following 9–bit format:
T = -25
°
C
SLOPE ACCUMULATOR
PRESET
COMPARE
LOW TEMPERATURE
COEFFICIENT OSCILLATOR
COUNTER
PRESET
=0
TEMPERATURE REGISTER
HIGH TEMPERATURE
COEFFICIENT OSCILLATOR
COUNTER
=0
INC
STOP
SET/CLEAR
LSB
1
1
1
0
0
1
1
1
0
0
0
0
0
0
0
0
MSB
LSB