Datasheet
DS2413: 1-Wire Dual Channel Addressable Switch
5 of 18
64-BIT LASERED ROM
Each DS2413 has a unique ROM Registration Number that is 64 bits long, as shown in Figure 3. The first eight bits
are a 1-Wire family code. The next 48 bits are a unique serial number. The last eight bits are a CRC (Cyclic
Redundancy Check) of the first 56 bits. 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
8
+ X
5
+ X
4
+ 1. Additional information about
the Dallas 1-Wire CRC is available in Application Note 27. The shift register bits are initialized to zero. Then
starting with the LSB 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 is entered. After the 48th bit of the serial number has been entered, the shift
register contains the CRC value. Shifting in the eight bits of CRC should return the shift register to all zeros.
Figure 2. Hierarchical Structure for 1-Wire Protocol
DS2413
Command
Level:
1-Wire ROM Function
Commands (see Figure 10)
DS2413-specific
PIO Function Commands
(see Figure 6)
Available
Commands:
Read ROM
Match ROM
Search ROM
Skip ROM
Resume
Overdrive Skip
Overdrive Match
PIO Access Read
PIO Access Write
Data Field
Affected:
64-bit Reg. #, RC-Flag
64-bit Reg. #, RC-Flag
64-bit Reg. #, RC-Flag
RC-Flag
RC-Flag
RC-Flag, OD-Flag
64-bit Reg. #, RC-Flag,
OD-Flag
PIO Pins
PIO Pins
Command
Codes:
33h
55h
F0h
CCh
A
5h
3Ch
69h
F5h
5Ah
Figure 3. 64-Bit LASERED ROM
MSB LSB
8-Bit CRC Code 48-Bit Serial Number
8-Bit Family Code (3Ah)
MSB LSB MSB LSB MSB LSB
Figure 4. 1-Wire CRC Generator
X
0
X
1
X
2
X
3
X
4
X
5
X
6
X
7
X
8
Polynomial = X
8
+ X
5
+ X
4
+ 1
1
st
STAGE
2
nd
STAGE
3
rd
STAGE
4
th
STAGE
6
th
STAGE
5
th
STAGE
7
th
STAGE
8
th
STAGE
INPUT DATA