DS2406 Maxim, DS2406 Datasheet - Page 4

• Manufacturer Part Number: DS2406
• Description: The DS2406 Dual Addressable Switch Plus Memory offers a simple way to remotely control a pair of open drain transistors and to monitor the logic level at each transistor's output via the 1-Wire® bus for closed loop control
• Manufacturer: Maxim

PARASITE POWER
The DS2406 can derive its power entirely from the 1-Wire bus by storing energy on an internal capacitor
during periods of time when the signal line is high. During low times the device continues to operate off
of this “parasite” power source until the 1-Wire bus returns high to replenish the parasite (capacitor)
supply. In applications where the device may be temporarily disconnected from the 1-Wire bus or where
the low-times of the 1-Wire bus may be very long the V
supply to maintain the device status.
When writing to the EPROM memory, the 1-Wire communication occurs at normal voltage levels and
then is pulsed momentarily to the programming voltage to cause the selected EPROM bits to be
programmed. The bus master must be able to provide 12V and 10mA to adequately program the EPROM
portions of the device. During programming, only EPROM-based devices are allowed to be present on
the 1-Wire bus.
64-BIT LASERED ROM
Each DS2406 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
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, 1 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 8 bits of CRC
should return the shift register to all zeros. The 64-bit ROM and the 1-Wire Function Control section
allow the DS2406 to operate as a 1-Wire device and follow the protocol detailed in the section “1-Wire
Bus System”.
64-BIT LASERED ROM Figure 3
1-WIRE CRC GENERATOR Figure 4
X
0
STAGE
MSB
MSB
1ST
8-Bit CRC Code
X
1
STAGE
2ND
X
2
STAGE
3RD
LSB
X
3
STAGE
MSB
4TH
Polynomial = X
48-Bit Serial Number
8
+ X
8
5
X
4 of 32
4
+ X
+ X
STAGE
5TH
5
4
+ X
+ 1. Additional information about the Dallas 1-
CC
4
pin may be connected to an external voltage
+ 1
LSB
X
5
STAGE
MSB
6TH
8-Bit Family Code (12h)
R
INPUT DATA
X
6
STAGE
S
7TH
X
7
STAGE
8TH
LSB
LSB
X
8