Rainbow Electronics DS2422 - Manual (Page 41)

DS2422
41 of 48
Master-to-Slave
For a write-one time slot, the voltage on the data line must have crossed the V
TH
threshold before the write-one
low time t
W1LMAX
is expired. For a write-zero time slot, the voltage on the data line must stay below the V
TH
threshold until the write-zero low time t
W0LMIN
is expired. For most reliable communication the voltage on the data
line should not exceed V
ILMAX
during the entire t
W0L
or t
W1L
window. After the V
TH
threshold has been crossed, the
DS2422 needs a recovery time t
REC
before it is ready for the next time slot.
Figure 16. Read/Write Timing Diagram
Write-One Time Slot
RESISTOR MASTER
V
PUP
V
IHMASTER
V
TH
V
TL
V
ILMAX
0V
t
F
t
SLOT
t
W1L
e
Write-Zero Time Slot
RESISTOR MASTER
t
REC
V
PUP
V
IHMASTER
V
TH
V
TL
V
ILMAX
0V
t
F
t
SLOT
t
W0L
Read-Data Time Slot
RESISTOR MASTER DS2422
t
REC
V
PUP
V
IHMASTER
V
TH
V
TL
V
ILMAX
0V
Master
Sampling
Window
d t
F
t
SLOT
t
RL
t
MSR
Slave-to-Master
A read-data time slot begins like a write-one time slot. The voltage on the data line must remain below V
TL
until the
read low time t
RL
is expired. During the t
RL
window, when responding with a 0, the DS2422 will start pulling the data
line low; its internal timing generator determines when this pulldown ends and the voltage starts rising again. When
responding with a 1, the DS2422 will not hold the data line low at all, and the voltage starts rising as soon as t
RL
is
over.