Rainbow-electronics DS1722 Manual de usuario descargar pdf (Pagina 4)

DS1722

4 of 13

The resolution of the temperature conversion is configurable (8, 9, 10, 11, or 12 bits), with 9-bit readings

the default state. This equates to a temperature resolution of 1.0°C, 0.5°C, 0.25°C, 0.125°C, or 0.0625°C.

Following each conversion, thermal data is stored in the thermometer register in two’s complement

format; the information can be retrieved over the SPI or 3-wire interface with the address set to the

temperature register, 01h (LSB) and then 02h (MSB). Table 2 describes the exact relationship of output

data to measured temperature. The table assumes the DS1722 is configured for 12-bit resolution; if the

device is configured in a lower resolution mode, those bits will contain 0s. The data is transmitted

serially over the digital interface, MSb first for SPI communication and LSb first for 3-wire

communication. The MSb of the temperature register contains the “sign” (S) bit, denoting whether the

temperature is positive or negative. For Fahrenheit usage, a lookup table or conversion routine must be

used.

Temperature/Data Relationships Table 2

Address

Location

02h

MSb (unit = °C) LSb

-1

-2

-3

-4

000001h

TEMPERATURE

DIGITAL OUTPUT

(BINARY)

DIGITAL OUTPUT

(HEX)

+120°C

0111 1000 0000 0000 7800h

+25.0625°C

0001 1001 0001 0000 1910h

+10.125°C

0000 1010 0010 0000 0A20h

+0.5°C

0000 0000 1000 0000 0080h

0°C

0000 0000 0000 0000 0000h

-0.5°C

1111 1111 1000 0000 FF80h

-10.125°C

1111 0101 1110 0000 F5E0h

-25.0625°C

1110 0110 1111 0000 E6F0h

-55°C

1100 1001 0000 0000 C900h

OPERATION-Programming

The area of interest in programming the DS1722 is the Configuration register. All programming is done

via the SPI or 3-wire communication interface by selecting the appropriate address of the desired register

location. Table 3 illustrates the addresses for the two registers (configuration and temperature) of the

DS1722.

Read Address Write Address Active Register

00h 80h Configuration

01h No access Temperature LSB

02h No access Temperature MSB

1 2 3 4 5 6 7 8 9 ... 12 13

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