Datasheet

Read/Write Time Slots
The bus master writes data to the device during write time
slots and reads data from the device during read time
slots. One bit of data is transmitted over the 1-Wire bus
per time slot.
Write Time Slots
There are two types of write time slots: write-one time
slots and write-zero time slots. The bus master uses a
write-one time slot to write a logic 1 to the device and a
write-zero time slot to write a logic 0 to the device. All write
time slots must be a minimum of 60µs in duration with a
minimum of a 1µs recovery time between individual write
slots. Both types of write time slots are initiated by the
master pulling the 1-Wire bus low (Figure9).
To generate a write-one time slot, after pulling the 1-Wire
bus low, the bus master must release the 1-Wire bus
within 15µs. When the bus is released, the 5kΩ pullup
resistor pulls the bus high. To generate a write-zero time
slot, after pulling the 1-Wire bus low, the bus master must
continue to hold the bus low for the duration of the time
slot (at least 60µs).
The device samples the 1-Wire bus during a window that lasts
from 15µs to 60µs after the master initiates the write time slot.
If the bus is high during the sampling window, a 1 is written to
the device. If the line is low, a 0 is written to the device.
Figure 9. Read/Write Time Slot Timing Diagram
V
PU
1-Wire BUS
START
OF SLOT
START
OF SLOT
60µs < T
X
“0” < 120µs
1µs < t
REC
< ∞
1µs < t
REC
< ∞
> 1µs
> 1µs
MASTER SAMPLES
MASTER SAMPLES
> 1µs
15µs 15µs 30µs
MASTER WRITE-ZERO SLOT
DEVICE SAMPLES
MIN MAXTYP
DEVICE SAMPLES
MIN MAXTYP
MASTER WRITE-ONE SLOT
MASTER READ-ZERO SLOT MASTER READ-ONE SLOT
GND
V
PU
1-Wire BUS
GND
15µs 45µs 15µs
15µs 15µs 30µs
BUS MASTER PULLING LOW DEVICE PULLING LOW RESISTOR PULLUP
MAX31820PAR 1-Wire, Parasite-Power,
Ambient Temperature Sensor
www.maximintegrated.com
Maxim Integrated │ 17