DS2417 Maxim, DS2417 Datasheet - Page 3

• Manufacturer Part Number: DS2417
• Description: The DS2417 1-Wire Time Chip with Interrupt offers a simple solution for storing and retrieving vital time information with minimal hardware
• Manufacturer: Maxim

64-BIT LASERED ROM
Each DS2417 contains a unique ROM code that is 64 bits long. 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 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 Semiconductor 1-Wire Cyclic Redundancy Check is available in Application Note 27. The shift
register bits are initialized to zero. 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 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. The 64-bit ROM and
ROM Function Control section allow the DS2417 to operate as a 1-Wire device and follow the 1-Wire
protocol detailed in the section "1-Wire Bus System".
HIERARCHICAL STRUCTURE FOR 1-WIRE PROTOCOL Figure 2
64-BIT LASERED ROM Figure 3
MSB
MSB
Master
Command
Level
8-Bit CRC Code
Bus
Commands (see Figure 7)
1-Wire ROM Function
DS2417 specific
Function Commands
(see Figure 5)
LSB
MSB
1-Wire Bus
48-Bit Serial Number
Available
Commands
Read ROM
Match ROM
Search ROM
Skip ROM
Write Clock
Read Clock
DS2417
3 of 15
8
+ X
5
+ X
Data Fields
Affected
64-bit ROM
64-bit ROM
64-bit ROM
N/A
RTC Counter, Device Control
RTC Counter, Device Control
4
LSB
+ 1. Additional information about the
Other
Devices
MSB
8-Bit Family Code (27h)
LSB
LSB