DS2406P datasheet(23/30 Pages) DALLAS

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DS2406

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1-WIRE SIGNALING

The DS2406 requires strict protocols to ensure data integrity. The protocol consists of five types of

signaling on one line: Reset Sequence with Reset Pulse and Presence Pulse, Write 0, Write 1, Read Data

and Program Pulse. Except for the presence pulse the bus master initiates all these signals.

The initialization sequence required to begin any communication with the DS2406 is shown in Figure 14.

A reset pulse followed by a presence pulse indicates the DS2406 is ready to send or receive data. The bus

master transmits (TX) a reset pulse (tRSTL, minimum 480 µs). The bus master then releases the line and

goes into receive mode (RX). The 1-Wire bus is pulled to a high state via the pull-up resistor. After

detecting the rising edge on the data pin, the DS2406 waits (tPDH, 15-60 µs) and then transmits the

presence pulse (tPDL, 60-240 µs).

INITIALIZATION PROCEDURE “RESET AND PRESENCE PULSES” Figure 14

RESISTOR

MASTER

DS2406

MASTER RX "PRESENCE PULSE"

480 µs ≤ tRSTL < ∞*

480 µs ≤ tRSTH < ∞ (includes recovery time)

15 µs ≤ tPDH < 60 µs

60 ≤ tPDL < 240 µs

MASTER TX

"RESET PULSE"

VPULLUP

VPULLUP MIN

VIH MIN

VIL MAX

tRSTH

tRSTL

tPDH

tPDL

In order not to mask interrupt signaling by other devices on the 1-Wire bus, tRSTL + tR should

always be less than 960 µs. In a parasitically powered environment tRSTL should be limited to

maximum 5 ms. Otherwise the DS2406 may perform a power-on reset.

READ/WRITE TIME SLOTS

The definitions of write and read time slots are illustrated in Figure 15. The master initiates all time slots

by driving the data line low. The falling edge of the data line synchronizes the DS2406 to the master by

triggering an internal delay circuit. During write time slots, the delay circuit determines when the DS2406

will sample the data line. For a read data time slot, if a “0” is to be transmitted, the delay circuit

determines how long the DS2406 will hold the data line low. If the data bit is a “1”, the DS2406 will not

hold the data line low at all.

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