Rainbow Electronics DS1624 - Manual (Page 6)

DS1624
6 of 16
TEMPERATURE MEASURING CIRCUITRY Figure 4
Internally, this calculation is performed by the DS1624 to provide 0.03125
°
C resolution. The temperature
reading is provided in a 13–bit, two’s complement reading by issuing READ TEMPERATURE
command. Table 2 describes the exact relationship of output data to measured temperature. The data is
transmitted serially through the 2–wire serial interface, MSB first. The DS1624 can measure temperature
over the range of -55
°
C to +125
°
C in 0.03125
°
C increments. For Fahrenheit usage a lookup table or
conversion factor must be used.
TEMPERATURE/DATA RELATIONSHIPS Table 2
TEMP DIGITAL OUTPUT
(Binary)
DIGITAL OUTPUT
(Hex)
+125°C 01111101 00000000 7D00h
+25.0625°C 00011001 00010000 1910h
+½°C 00000000 10000000 0080h
+0°C 00000000 00000000 0070h
-½°C 11111111 10000000 FF80h
-25.0625°C 11100110 11110000 E6F0h
-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
DS1624 as either a single byte (with temperature resolution of 1
°
C) or as two bytes, the second byte
containing the value of the 5 least significant bits of the temperature reading as shown in Table 1. Note
that the remaining three bits of this byte are set to all 0’s.
SLOPE ACCUMULATOR
PRESET COMPARE
LOW TEMPERATURE
COEFFICIENT OSCILLATOR
COUNTER PRESET
=0 TEMPERATURE REGISTER
HIGH TEMPERATURE
COEFFICIENT OSCILLATOR
COUNTER
=0
INC
STOP
SET/CLEAR
LSB