Rainbow Electronics DS2415 - Manual (Page 2)

DS2415
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available until the ROM function protocol has been established. This protocol is described in the ROM
functions flow chart (Figure 7). The master must first provide one of four ROM function commands: 1)
Read ROM, 2) Match ROM, 3) Search ROM, 4) Skip ROM. After a ROM function sequence has been
successfully executed, the real-time clock functions are accessible and the master may then provide a real
time clock function command (Figure 5).
DETAILED PIN DESCRIPTION
PIN SYMBOL DESCRIPTION
1 GND Ground pin.
2 1-Wire Data input/output. Open drain.
3 V
DD
Internal power line. Connect a capacitor
4 V
BAT
Power input pin. 2.5V to 5.5V.
5, 6 X1, X2
Crystal pins. Connections for a standard 32.768kHz quartz crystal,
EPSON part number C-002RX or C-004R (be sure to request 6pF load
capacitance).
NOTE: X1 and X2 are very high-impedance nodes. It is recommended
that they and the crystal be guard-ringed with ground and that high
frequency signals be kept away from the crystal area. See Figure 10 and
Application Note 58 for details.
BLOCK DIAGRAM Figure 1
64-BIT LASERED ROM
Each DS2415 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 of the lasered ROM is generated using the polynomial X
8 + X 5 + X 4 + 1. Additional
information about the Dallas Semiconductor 1-Wire Cyclic Redundancy Check is available in the Book
of DS19xx iButton Standards
® . The 64-bit ROM and ROM Function Control section allow the DS2415 to
operate as a 1-Wire device and follow the 1-Wire protocol detailed in the section ”1-Wire Bus System.”