Rainbow-electronics DS1822-PAR Manual de usuario descargar pdf (Pagina 14)

DS1822-PAR

14 of 19

The DS1822-PAR samples the 1-wire bus during a window that lasts from 15 µs to 60 µs after the master

initiates the write time slot. If the bus is high during the sampling window, a 1 is written to the DS1822-

PAR. If the line is low, a 0 is written to the DS1822-PAR.

READ/WRITE TIME SLOT TIMING DIAGRAM Figure 12

READ TIME SLOTS

The DS1822-PAR can only transmit data to the master when the master issues read time slots. Therefore,

the master must generate read time slots immediately after issuing a Read Scratchpad [BEh] command, so

that the DS1822-PAR can provide the requested data. In addition, the master can generate read time slots

after issuing a Recall E

[B8h] command to find out the recall status as explained in the DS1822-PAR

FUNCTION COMMAND section.

All read time slots must be a minimum of 60 µs in duration with a minimum of a 1 µs recovery time

between slots. A read time slot is initiated by the master device pulling the 1-wire bus low for a

minimum of 1 µs and then releasing the bus (see Figure 12). After the master initiates the read time slot,

the DS1822-PAR will begin transmitting a 1 or 0 on bus. The DS1822-PAR transmits a 1 by leaving the

bus high and transmits a 0 by pulling the bus low. When transmitting a 0, the DS1822-PAR will release

the bus by the end of the time slot, and the bus will be pulled back to its high idle state by the pullup

LINE TYPE LEGEND

Bus master pulling low DS1822-PAR pulling low

Resistor pullup

µµ

µs

µµ

µs

GND

1-WIRE BUS

µµ

µs < T

“0” < 120

1 µ

µµ

µs < T

REC

< ∞

DS1822-PAR samples

MIN TYP MA

µµ

µs

µµ

µs

> 1

µµ

µs

MASTER WRITE “0” SLOT MASTER WRITE “1” SLOT

DS1822-PAR samples

MIN TYP MA

GND

1-WIRE BUS

µµ

µs

MASTER READ “0” SLOT MASTER READ “1” SLOT

Master samples

START

OF SLOT

START

OF SLOT

> 1

µµ

µs

1 µ

µµ

µs < T

REC

< ∞

µµ

µs

µµ

µs

µµ

µs

µµ

µs

> 1

µµ

µs

1 2 ... 9 10 11 12 13 14 15 16 17 18 19

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Rainbow-electronics DS1822-PAR Manual de usuario Pagina 14

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