Rainbow Electronics DS1972 - Manual (Page 19)

DS1972: 1024-Bit EEPROM iButton
19 of 23
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 the 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 DS1972 needs a recovery time t
REC
before it is ready for the next time slot.
Figure 11. 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 DS1972
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