DS2407 datasheet(2/31 Pages) DALLAS

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DS2407

012099 2/31

ORDERING INFORMATION

DS2407

TO–92 package

DS2407P

6–pin TSOC package

DS2407T

Tape & Reel version of DS2407

DS2407V

Tape & Reel version of DS2407P

DS2407X

Chip Scale Pkg., Tape & Reel

ADDRESSABLE SWITCHTM DESCRIPTION

The DS2407 Dual Addressable Switch Plus Memory is

a pair of open drain N–channel transistors that can be

turned on or off via the 1–Wire bus. Alternatively, either

open drain output can serve as a logic input that can be

monitored via the same 1–Wire bus. In addition, the

device has 1024 bits of EPROM to store relevant

information such as switch function, physical location,

etc. The device is addressed by matching its individual

64–bit factory–lasered registration number. The 64–bit

number consists of an 8–bit family code, a unique 48–bit

serial number, and an 8–bit cyclic redundancy check.

Communication with the DS2407 follows the standard

Dallas Semiconductor 1–Wire protocol and can be

accomplished with a single port pin of a microcontroller.

Multiple DS2407 devices can reside on a common

1–Wire bus creating a MicroLAN. The network control-

ler circuitry is embedded within the chip including a

search algorithm to determine the identity of each

DS2407 on the network. The open drain outputs (PIO

pins) for each DS2407 on the MicroLAN can be inde-

pendently switched on or off whether there is one or

many devices sharing the same 1–Wire bus. The logic

level of the PIO pins for each device on the MicroLAN

can also be individually sensed and reported to the bus

master. The device also supports a Conditional Search

command to identify and access devices that qualify for

certain user–specified conditions. Qualification may be

the status of a PIO–pin, the state of the output transistor

or a latched activity flag.

OVERVIEW

The DS2407 Dual Addressable Switch Plus Memory

provides a means for assigning an electronically read-

able identification to a particular node or location with

additional control capability provided by two open–drain

N–channel MOSFETs that can be remotely switched

and sensed via communication over the 1–Wire bus

(Figure 1). The DS2407 contains a factory–lasered reg-

istration number that includes a unique 48–bit serial

number, an 8–bit CRC, and an 8–bit family code (12h).

The 64–bit ROM portion of the DS2407 not only creates

an absolutely unique electronic identification for the

device itself but also is a means to locate and obtain or

change the state of the switches that are associated

with the 64–bit ROM.

The device derives its power entirely from the 1–Wire

bus by storing energy on an internal capacitor during

periods of time when the signal line is high and contin-

ues to operate off of this “parasite” power source during

the low times of the 1–Wire line until it returns high to

replenish the parasite (capacitor) supply. For applica-

tions in feeder–networks where the low–times of the

1–Wire line may be very long, the VCC pin may be con-

nected to an external voltage supply to operate the

device.

The DS2407 uses the standard Dallas Semiconductor

1–Wire protocol for data transfers (Figure 2), with all

data being read and written least significant bit first.

Communication to and from the DS2407 requires a

single bi–directional line that is typically a port pin of a

microcontroller. The 1–Wire bus master (microcontrol-

ler) must first issue one of five ROM function com-

mands: 1) Read ROM, 2) Match ROM, 3) Search ROM,

4) Skip ROM, or 5) Conditional Search ROM. These

commands operate on the 64–bit lasered ROM portion

of each device and can singulate a specific device if

many are present on the 1–Wire line as well as indicate

to the bus master how many and what type of each

device is present. After a ROM function command is

successfully executed, the open–drain outputs can be

switched or sensed, or the contents of the memory can

be read or written via the 1–Wire bus. Writing the 1024

bits of data memory or writing to the EPROM sections of

the status memory requires a 12V programming pulse.

When programming the DS2407, only EPROM–based

devices are allowed to be present on the 1–Wire line.

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