Rainbow-electronics DS1920 Manual do Utilizador descarregar pdf (Página 15)

DS1920

15 of 22

MEMORY AND CONTROL FUNCTIONS FLOW CHART (cont’d) Figure 9

1-WIRE SIGNALING

The DS1920 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 Strong Pullup. All these signals except Presence Pulse are initiated by the bus master. The

initialization sequence required to begin any communication with the DS1920 is shown in Figure 10. A

Reset Pulse followed by a Presence Pulse indicates the DS1920 is ready to accept a ROM command. The

bus master transmits (TX) a Reset Pulse (t

RSTL

, 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 pullup resistor. After

detecting the rising edge on the 1-Wire line, the DS1920 waits (t

PDH

, 15-60 µs) and then transmits the

Presence Pulse (t

PDL

, 60-240 µs).

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