DS2405

13 of 15

102299

READ/WRITE TIMING DIAGRAM Figure 6 (cont.)

Read-Data Time Slot

60

µs ≤t

µs

1

µs ≤t

µs

0

≤t

µs

1

µs ≤t

∞

µs

µs

CRC GENERATION

To validate the data transmitted from the DS2405, the bus master may generate a CRC value from the

data as it is received. This generated value is compared to the value stored in the last 8 bits of the

DS2405. If the two CRC values match, the transmission is error-free.

The equivalent polynomial function of this CRC is:

CRC = x

For more details, see the Book of DS19xx iButton Standards.

CUSTOM DS2405

Customization of a portion of the unique 48-bit serial number by the customer is available. Dallas

Semiconductor will register and assign a specific customer ID in the 12 most significant bits of the 48-bit

field. The next most significant bits are selectable by the customer as a starting value, and the least

significant bits are non-selectable and will be automatically incremented by one. Certain quantities and

conditions apply for these special order parts. Contact your Dallas Semiconductor sales representative for

more information.

RESISTOR

MASTER

DS2405