Temperature measuring circuitry figure 2, Temperature/data relationships table 1 – Rainbow Electronics DS1620 User Manual

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DS1620

3 of 13

TEMPERATURE MEASURING CIRCUITRY Figure 2

This calculation is done inside the DS1620 to provide 0.5

C resolution. The temperature reading is

provided in a 9–bit, two’s complement reading by issuing a READ TEMPERATURE command. Table 1
describes the exact relationship of output data to measured temperature. The data is transmitted serially
through the 3–wire serial interface, LSB first. The DS1620 can measure temperature over the range of
-55

C to +125

C in 0.5

C increments. For Fahrenheit usage, a lookup table or conversion factor must be

used.

TEMPERATURE/DATA RELATIONSHIPS Table 1

TEMP

DIGITAL OUTPUT

(Binary)

DIGITAL OUTPUT

(Hex)

+125°C

0 11111010

00FA

+25°C

0 00110010

0032h

+½°C

0 00000001

0001h

+0°C

0 00000000

0000h

-½°C

1 11111111

01FFh

-25°C

1 11001110

01CEh

-55°C

1 10010010

0192h

Since data is transmitted over the 3–wire bus LSB first, temperature data can be written to/read from the

DS1620 as either a 9–bit word (taking

RST

low after the 9

(MSB) bit), or as two transfers of 8–bit

SLOPE ACCUMULATOR

PRESET

COMPARE

LOW TEMPERATURE

COEFFICIENT OSCILLATOR

COUNTER

PRESET

TEMPERATURE REGISTER

HIGH TEMPERATURE

COEFFICIENT OSCILLATOR

COUNTER

INC

STOP

SET/CLEAR
LSB