Rainbow Electronics DS2405 - Manual (Page 13)

DS2405
13 of 15
READ/WRITE TIMING DIAGRAM Figure 6 (cont.)
Read-Data Time Slot
60 ms £ t
SLOT
< 120 ms
1 ms £ t
LOWR
< 15 ms
0 £ t
RELEASE
< 45 ms
1 ms £ t
REC
< ¥
t
RDV
= 15 ms
t
SU
< 1 ms
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 8 + x 5 + x 4 + 1
For more details, see the Book of DS19xx iButton Standards.
RESISTOR
MASTER
DS2405