Rainbow Electronics DS2401 User Manual

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DS2401

Silicon Serial Numbe

FEATURES

§ Upgrade and drop-in replacement for DS2400

— Extended 2.8 to 6.0 voltage range
— Multiple DS2401s can reside on a
common 1-Wireâ Net

§ Unique, factory-lasered and tested 64-bit

registration number (8-bit family code + 48­bit serial number + 8-bit CRC tester);
guaranteed no two parts alike

§ Built-in multidrop controller ensures

compatibility with other 1-Wire Net

products

§ 8-bit family code specifies DS2401

communications requirements to reader

§ Presence Pulse acknowledges when the

reader first applies voltage

§ Low-cost TO-92, SOT-223, and TSOC

surface mount packages

§ Reduces control, address, data, and power to

a single pin

§ Zero standby power required

§ Directly connects to a single port pin of a

microprocessor and communicates at up to

16.3kbits/s

§ TO-92 Tape & Reel version with leads bent

to 100mil spacing (default) or with straight
leads (DS2401T-SL)

§ Applications

— PCB Identification
— Network Node ID
— Equipment Registration

§ Operates over industrial temperature range of

-40°C to +85°C

PIN ASSIGNMENT

TO-92

DALLAS

DS2401

1 2 3

2 3

BOTTOM VIEW

TSOC PACKAGE

TOP VIEW

3.7mm x 4.0mm x 1.5mm

TOP VIEW

See Mech. Drawings

Section

PIN DESCRIPTION

TO-92/SOT-223 TSOC

Pin 1 Ground Ground
Pin 2 Data (DQ) Data (DQ)
Pin 3 No Connect No Connect
Pin 4 Ground No Connect
Pin 5-6

-

No Connect

ORDERING INFORMATION

DS2401 TO-92 Package
DS2401Z SOT-223 Surface Mount Package
DS2401/T&R Tape & Reel of DS2401
DS2401T-SL Like DS2401T but Straight Leads
DS2401Z/T&R Tape & Reel of DS2401Z
DS2401P TSOC Surface Mount Package
DS2401P/T&R Tape & Reel of DS2401P
DS2401X1 Chip Scale Pkg., Tape & Reel

1-Wire is a registered trademark of Dallas Semiconductor.

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DS2401

DESCRIPTION

The DS2401 enhanced Silicon Serial Number is a low-cost, electronic registration number that provides
an absolutely unique identity which can be determined with a minimal electronic interface (typically, a
single port pin of a microcontroller). The DS2401 consists of a factory-lasered, 64-bit ROM that includes
a unique 48-bit serial number, an 8-bit CRC, and an 8-bit Family Code (01h). Data is transferred serially
via the 1-Wire protocol that requires only a single data lead and a ground return. Power for reading and
writing the device is derived from the data line itself with no need for an external power source. The
DS2401 is an upgrade to the DS2400. The DS2401 is fully reverse-compatible with the DS2400 but
provides the additional multi-rop capability that enables many devices to reside on a single data line. The
familiar TO-92, SOT-223 or TSOC package provides a compact enclosure that allows standard assembly
equipment to handle the device easily.

OPERATION

The DS2401’s internal ROM is accessed via a single data line. The 48-bit serial number, 8-bit family
code and 8-bit CRC are retrieved using the Dallas 1-Wire protocol. This protocol defines bus transactions
in terms of the bus state during specified time slots that are initiated on the falling edge of sync pulses
from the bus master. All data is read and written least significant bit first.

1-WIRE BUS SYSTEM

The 1-Wire bus is a system which has a single bus master system and one or more slaves. In all instances,
the DS2401 is a slave device. The bus master is typically a microcontroller. The discussion of this bus
system is broken down into three topics: hardware configuration, transaction sequence, and 1-Wire
signaling (signal type and timing). For a more detailed protocol description, refer to Chapter 4 of the
Book of DS19xx iButton® Standards.

Hardware Configuration

The 1-Wire bus has only a single line by definition; it is important that each device on the bus be able to
drive it at the appropriate time. To facilitate this, each device attached to the 1-Wire bus must have an
open-drain connection or 3-state outputs. The DS2401 is an open-drain part with an internal circuit
equivalent to that shown in Figure 2. The bus master can be the same equivalent circuit. If a bidirectional
pin is not available, separate output and input pins can be tied together. The bus master requires a pullup
resistor at the master end of the bus, with the bus master circuit equivalent to the one shown in Figure 3.
The value of the pullup resistor should be approximately 5kW for short line lengths. A multidrop bus
consists of a 1-Wire bus with multiple slaves attached. The 1-Wire bus has a maximum data rate of

16.3kbits per second.

The idle state for the 1-Wire bus is high. If, for any reason, a transaction needs to be suspended, the bus
MUST be left in the idle state if the transaction is to resume. If this does not occur and the bus is left low
for more than 120ms, one or more of the devices on the bus may be reset.

DS2401 MEMORY MAP Figure 1

8-Bit CRC Code 48-Bit Serial Number 8-Bit Family Code (01h)

MSB LSB MSB LSB MSB LSB

iButton is a registered trademark of Dallas Semiconductor.

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DS2401 EQUIVALENT CIRCUIT Figure 2

BUS MASTER CIRCUIT Figure 3

A) Open Drain

DS2401

See note

To data connection
of DS2401

B) Standard TTL

See note

To data connection
of DS2401

Note:
Depending on the 1-Wire communication speed and the bus load characteristics, the optimal pullup
resistor (R

) value will be in the 1.5kW to 5kW range.

PU

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