DS2408 Maxim, DS2408 Datasheet - Page 25

• Manufacturer Part Number: DS2408
• Description: The DS2408 is an 8-channel, programmable I/O 1-Wire® chip
• Manufacturer: Maxim

Read/Write Time Slots
Data communication with the DS2408 takes place in time slots, which carry a single bit each. Write time
slots transport data from bus master to slave. Read time slots transfer data from slave to master. The
definitions of the write and read time slots are illustrated in Figure 14.
All communication begins with the master pulling the data line low. As the voltage on the 1-Wire line
falls below the threshold V
base creates a slave-sampling window, which stretches from t
line at the sampling point determines whether the DS2408 decodes the time slot as 1 or 0.
Master-to-Slave
For a write-one time slot, the voltage on the data line must have crossed the V
write-one low time t
below the V
communication, the voltage on the data line should not exceed V
After the V
the next time slot.
Figure 14. READ/WRITE TIMING DIAGRAM
Write-One Time Slot
Write-Zero Time Slot
V
V
THMAX
IHMASTER
IHMASTER
V
V
THMIN
V
V
ILMAX
ILMAX
V
V
V
V
PUP
PUP
0V
0V
TH
TH
TL
TL
threshold has been crossed, the DS2408 needs a recovery time t
t
W1LMAX
threshold until the write-zero low time t
F
t
F
TL
has expired. For a write-zero time slot, the voltage on the data line must stay
t
W1L
, the DS2408 starts its internal time base. The tolerance of the slave time
t
t
SLSMIN
SLSMIN
ε
t
W0L
25 of 39
t
Sampling
Sampling
SLSMAX
DS2408
Window
DS2408
Window
t
SLSMAX
SLSMIN
W0LMIN
ILMAX
to t
ε
t
has expired. For most reliable
SLOT
SLSMAX
during the entire t
t
SLOT
t
REC
. The voltage on the data
THMAX
REC
before it is ready for
threshold after the
W0L
window.
DS2408