Rainbow-electronics DS28EA00 Manual de usuario descargar pdf (Pagina 8)

DS28EA00 1-Wire Digital Thermometer with Sequence Detect and PIO

8 of 29

The temperature reading is in °C using a 16-bit sign-extended two’s complement format. Table 1 shows examples

of temperature and the corresponding data for 12-bit resolution. With two’s complement, the sign bit is set if the

value is negative. If the device is configured for 12-bit resolution, all bits in the LS byte are valid; for a reduced

resolution, bit 0 (11 bit mode), bits 0 to 1 (10 bit mode), and bits 0 to 2 (9 bit mode) are undefined.

Table 1. Temperature/Data Relationship

TEMPERATURE

DIGITAL OUTPUT

(BINARY)

DIGITAL OUTPUT

(HEX)

+85°C* 0000 0101 0101 0000 0550h

+25.0625°C 0000 0001 1001 0001 0191h

+10.125°C 0000 0000 1010 0010 00A2h

+0.5°C 0000 0000 0000 1000 0008h

0°C 0000 0000 0000 0000 0000h

-0.5°C 1111 1111 1111 1000 FFF8h

-10.125°C 1111 1111 0101 1110 FF5Eh

-25.0625°C 1111 1110 0110 1111 FE6Fh

-40°C 1111 1101 1000 0000 FD80h

*The power-on reset value of the temperature readout register is +85°C.

Temperature Alarm Registers

ADDR bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

2 S 2

High Alarm (TH)

3 S 2

Low Alarm (TL)

The result of a temperature conversion is automatically compared to the values in the alarm registers to determine

whether an alarm condition exists. Alarm thresholds are represented as two’s complement number. With 8 bits

available for sign and value, alarm thresholds can be set in increments of 1°C. An alarm condition exists if a

temperature conversion results in a value that is either higher than or equal to the value stored in the TH register

or lower than or equal to the value stored in the TL register. If a temperature alarm condition exists, the device

will respond to the Conditional Search command. The alarm condition is cleared if a subsequent temperature

conversion results in a temperature reading within the boundaries defined by the data in the TH and TL registers.

Configuration Register

ADDR b7 b6 b5 b4 b3 b2 b1 b0

4 0 R1 R0 1 1 1 1 1

The functional assignments of the individual bits are explained in the table below. Bits 0 to 4 and bit 7 have no

function; they cannot be changed by the user. As a factory default, the device operates in 12-bit resolution.

BIT DESCRIPTION BIT(S) DEFINITION

R0, R1: Temperature

Converter Resolution

b5, b6

These bits control the resolution of the temperature

converter. The codes are as follows:

R1 R0

0 0 9 bits

0 1 10 bits

1 0 11 bits

1 1 12 bits

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 28 29

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