READ/WRITE TIMING DIAGRAM (cont’d) Figure 6
Write-zero Time Slot
DS2401
Read-data Time Slot
60 µs ≤tLOW0 < tSLOT < 120 µs
1 µs ≤tREC < ∞
RESISTOR
MASTER
DS2401
60 µs ≤tSLOT < 120 µs
1 µs ≤tLOWR < 15 µs
0 ≤tRELEASE < 45 µs
1 µs ≤tREC < ∞
tRDV = 15 µs
tSU < 1µs
CRC GENERATION
To validate the data transmitted from the DS2401, 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
DS2401. If the two CRC values match, the transmission is error-free.
The equivalent polynomial function of this CRC is: CRC = x8 + x5 + x4 + 1. For more details, see the
Book of DS19xx iButton Standards.
CUSTOM DS2401
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 custom parts. Contact your Dallas Semiconductor sales representative for more
information.
8 of 10
102199