DS1822

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1-WIRE SIGNALING

The DS1822 uses a strict 1-Wire communication protocol to insure data integrity. Several signal types are

defined by this protocol: reset pulse, presence pulse, write 0, write 1, read 0, and read 1. All of these

signals, with the exception of the presence pulse, are initiated by the bus master.

INITIALIZATION PROCEDURE: RESET AND PRESENCE PULSES

All communication with the DS1822 begins with an initialization sequence that consists of a reset pulse

from the master followed by a presence pulse from the DS1822. This is illustrated in Figure 13. When the

DS1822 sends the presence pulse in response to the reset, it is indicating to the master that it is on the bus

and ready to operate.

low for a minimum of 480

When the bus is released, the 5k pullup resistor pulls the 1-Wire bus high. When the DS1822 detects this

rising edge, it waits 15

ms to 60ms and then transmits a presence pulse by pulling the 1-Wire bus low for

60

ms to 240ms.

INITIALIZATION TIMING Figure 13

READ/WRITE TIME SLOTS

The bus master writes data to the DS1822 during write time slots and reads data from the DS1822 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 1” time slots and “Write 0” time slots. The bus master

uses a Write 1 time slot to write a logic 1 to the DS1822 and a Write 0 time slot to write a logic 0 to the

DS1822. All write time slots must be a minimum of 60

ms in duration with a minimum of a 1ms recovery

time between individual write slots. Both types of write time slots are initiated by the master pulling the

1-Wire bus low (see Figure 14).

To generate a Write 1 time slot, after pulling the 1-Wire bus low, the bus master must release the 1-Wire

bus within 15

ms. When the bus is released, the 5k pullup resistor will pull the bus high. To generate a

Write 0 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 60

ms).

LINE TYPE LEGEND

Bus master pulling low

DS1822 pulling low

Resistor pullup

GND

1-WIRE BUS

480

ms minimum

480

ms minimum

presence pulse

60-240

ms

DS1822

waits 15-60

ms