DS1963L

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DS1963L BLOCK DIAGRAM Figure 1

3V

Lithium

PARASITE POWER

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

whenever the I/O input is high. I/O will provide 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, lithium is conserved and 2) if the lithium is exhausted for any reason, the ROM may still be read

normally.

64-BIT LASERED ROM

Each DS1963L 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 3.) The 1-Wire CRC is generated using a polynomial generator consisting of a shift register and

XOR gates as shown in Figure 4. The polynomial is X

Dallas 1-Wire Cyclic Redundancy Check is available in the Book of DS19xx iButton Standards.

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 8

is entered. After the 48

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

DATA

LID

CONTACT

1-WIRE

FUNCTION

CONTROL

64-BIT

LASERED

ROM

PARASITE-POWERED

CIRCUITRY

256-BIT

SCRATCHPAD

MEMORY

FUNCTION

CONTROL

MEMORY

4096-BIT

SRAM

(256-BIT PAGES)

PAGE

WRITE CYCLE

COUNTERS