DS1923 查看數據表（PDF） - Dallas Semiconductor -> Maxim Integrated

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DS1923

Hygrochron Temperature/Humidity Logger iButton with 8kB Data Log Memory

Dallas Semiconductor -> Maxim Integrated 

DS1923: Hygrochron Temperature/Humidity Logger iButton with 8kB Data Log Memory

Figure 1. DS1923 BLOCK DIAGRAM

1-Wire

IO

Port

ROM

Function

Control

64-Bit

Lasered

ROM

Parasite

Powered

Circuitry

3V Lithium

Memory

Function

Control

256-Bit

Scratchpad

DS1923

32.768 kHz

Oscillator

Thermal

Sense

Humidity

Sensor and

ADC2

Internal

Timekeeping &

Control Reg. &

Counters

General-Purpose

SRAM

(512 Bytes)

Register Pages

(64 Bytes)

ADC1

Calibration Memory

(64 Bytes)

Control

Logic

Datalog

Memory

8K Bytes

PARASITE POWER

The block diagram (Figure 1) shows the parasite-powered circuitry. This circuitry “steals” power whenever the IO

input is high. IO provides sufficient power as long as the specified timing and voltage requirements are met. The

advantages of parasite power are two-fold: 1) by parasiting off this input, battery power is conserved, and 2) if the

battery is exhausted for any reason, the ROM may still be read.

64-BIT LASERED ROM

Each DS1923 contains a unique ROM code that is 64 bits long. The first 8 bits are a 1-Wire family code. The next

48 bits are a unique serial number. The last 8 bits are a CRC of the first 56 bits. See Figure 4 for details. The 1-

Wire CRC is generated using a polynomial generator consisting of a shift register and XOR gates as shown in

Figure 3. The polynomial is X8 + X5 + X4 + 1. Additional information about the Dallas 1-Wire Cyclic Redundancy

Check is available in Dallas Application Note 27.

The shift register bits are initialized to 0. Then starting with the least significant bit of the family code, one bit at a

time is shifted in. After the 8th bit of the family code has been entered, then the serial number followed by the

temperature range code is entered. After the range code has been entered, the shift register contains the CRC

value. Shifting in the 8 bits of CRC returns the shift register to all 0s.

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