DS1921 DALLAS [Dallas Semiconductor], DS1921 Datasheet - Page 31

• Manufacturer Part Number: DS1921
• Description: High-Resolution Thermochron iButton
• Manufacturer: DALLAS [Dallas Semiconductor]

READ/WRITE TIMING DIAGRAM Figure 15
Write-One Time Slot
Write-Zero Time Slot
Read-Data Time Slot
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
DS1921H/Z will start pulling the data line low; its internal timing generator determines when this pull-
down ends and the voltage starts rising again. When responding with a 1, the DS1921H/Z will not hold
the data line low at all, and the voltage starts rising as soon as t
The sum of t
other side define the master sampling window (t
read from the data line. For most reliable communication, t
master should read close to but no later than t
wait until t
for the next time slot.
TL
until the read low time t
V
V
V
SLOT
IHMASTER
IHMASTER
IHMASTER
V
V
V
RL
V
V
V
ILMAX
ILMAX
ILMAX
V
V
V
V
V
V
PUP
PUP
PUP
0V
0V
0V
is expired. This guarantees sufficient recovery time t
TH
TH
TH
+
TL
TL
TL
t
F
(rise rime) on one side and the internal timing generator of the DS1921H/Z on the
t
t
F
F
RESISTOR
RESISTOR
RESISTOR
t
RL
t
W1L
RL
is expired. During the t
Sampling
Window
Master
t
W0L
t
MSR
MSRMAX
MSRMIN
31 of 44
MASTER
MASTER
MASTER
t
SLOT
. After reading from the data line, the master must
t
t
SLOT
SLOT
to t
RL
MSRMAX
RL
RL
window, when responding with a 0, the
should be as short as permissible and the
is over.
) in which the master must perform a
REC
for the DS1921H/Z to get ready
t
REC
DS1921H/Z
t
REC
DS1921H/Z