Rainbow-electronics DS2409 Bedienungsanleitung PDF herunterladen (Seite 18)

DS2409

18 of 18

AC ELECTRICAL CHARACTERISTICS (-40°C to +85°C, V

= 5V ±10%)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Time Slot t

SLOT

60 120 µs

Write 1 Low Time t

LOW1

115µs10

Write 0 Low Time t

LOW0

60 120 µs

Read Low Time t

LOWR

115µs10

Read Data Valid t

RDV

15 µs 9

Release Time t

RELEASE

01545 µs

Read Data Setup t

1µs 6

Recovery Time t

REC

1µs

Reset Time High t

RSTH

480 µs 5

Reset Time Low t

RSTL

480 960 µs 7

Presence Detect High t

PDH

15 60 µs

Presence Detect Low t

PDL

60 240 µs

NOTES:

1. All voltages are referenced to ground.

2. Measured with outputs open.

3. V

PUP

= external pullup voltage.

4. Input load is to ground.

5. An additional reset or communication sequence cannot begin until the reset high time has expired.

6. Read data setup time refers to the time the bus master must pull the I/O line low to read a bit. Data is

guaranteed to be valid within 1 µs of this falling edge.

7. The reset low time (t

RSTL

) should be restricted to a maximum of 960 µs, to allow interrupt signaling,

otherwise, it could mask or conceal interrupt pulses. The DS2409 may perform a power-on reset cycle

and deactivate both 1-Wire outputs if the 1-Wire input is low for minimum 8 ms. A low time of 12 ms

or more will always cause a power-on reset cycle.

8. The main output has a slew rate controlled output. The indicated current is a DC value. The sink

current typically reaches 80% of its DC value 1 µs after turning on the transistor.

9. The optimal sampling point for the master is as close as possible to the end time of the 15µs t

RDV

period without exceeding t

RDV

. For the case of a Read-One Time Slot, this maximizes the amount of

time for the pull-up resistor to recover to a high level. For a Read-Zero Time Slot, it ensures that a

read will occur before the fastest 1-Wire device(s) release the line.

10. The duration of the low pulse sent by the master should be a minimum of 1µs with a maximum value

as short as possible to allow time for the pull-up resistor to recover the line to a high level before the

1-Wire device samples in the case of a Write-One Time or before the master samples in the case of a

Read-One Time.

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