Rainbow Electronics DS28EA00 User Manual

1-Wire Digital Thermomete

DS28EA00

with Sequence Detect and PIO

www.maxim-ic.com

GENERAL DESCRIPTION

The DS28EA00 is a digital thermometer with 9-bit (0.5 °C) to 12-bit (1/16 °C) resolution and alarm function with nonvolatile (NV), user-programmable upper and lower trigger points. Each DS28EA00 has its unique 64-bit registration number that is factoryprogrammed into the chip. Data is transferred serially through the 1-Wire

protocol, which requires only one data line and a ground for communication. The improved 1-Wire front end with hysteresis and glitch filter enables the DS28EA00 to perform reliably in large 1-Wire networks. Unlike other 1-Wire thermometers, the DS28EA00 has two additional pins to implement a sequence detect function. This feature allows the user to discover the registration numbers according to the physical device location in a chain, e.g., to measure the temperature in a storage tower at different height. If the sequence detect function is not needed, these pins can be used as generalpurpose input or output. The DS28EA00 can derive the power for its operation directly from the data line (“parasite power”), eliminating the need for an external power supply.

APPLICATIONS

Data Communication Equipment Process Temperature Monitoring HVAC Systems

TYPICAL OPERATING CIRCUIT

1-Wire Master

PX.

(Micro-

controller)

Schematic shows PIOs wired for sequence detect function.

Commands, Registers, and Modes are capitalized for clarity.

1-Wire is a registered trademark of Dallas Semiconductor.

Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device may be simultaneously available through various sales channels. For information about device errata, click here: www.maxim-ic.com/errata

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#1 #2

VDD

DS28EA00

PIOB PIOA

GND

PIOB PIOA

VDD

DS28EA00

GND

VDD

DS28EA00

PIOB PIOA

GND

SPECIAL FEATURES

 Digital Thermometer Measures Temperatures

from -40°C to +85°C

 Thermometer Resolution is User-Selectable

from 9 to 12 Bits

 Unique 1-Wire Interface Requires Only One

Port Pin for Communication

 Each Device has a Unique 64-Bit Factory-

Lasered Registration Number

 ROM Multidrop Capability Simplifies

Distributed Temperature-Sensing Applications

 Improved 1-Wire Interface with Hysteresis

and Glitch Filter

 User-Definable Nonvolatile (NV) Alarm

Threshold Settings/User Bytes

 Alarm Search Command to Quickly Identify

Devices Whose Temperature is Outside of Programmed Limits

 Standard and Overdrive 1-Wire Speed  Two General-Purpose Programmable IO (PIO)

Pins

 Chain Function Sharing the PIO Pins to

Detect Physical Sequence of Devices in Network

 Operating Range: 3.0V to 5.5V, -40°C to +85°C  Can be Powered from Data Line  8-Pin µSOP Package

ORDERING INFORMATION

PART TEMP RANGE PACKAGE

DS28EA00U+ -40 to +85°C 8-pin µSOP

DS28EA00U+T -40 to +85°C Tape & Reel

+ Denotes lead-free package.

PIN CONFIGURATION

IO NC NC

GND

8 pin µSOP

Package Outline Drawing 21-0036

PIOB PIOA NC

012907

DS28EA00 1-Wire Digital Thermometer with Sequence Detect and PIO

ABSOLUTE MAXIMUM RATINGS

IO Voltage to GND -0.5V, +6V IO Sink Current 20mA Maximum PIOA or PIOB Pin Current 20mA Maximum Current Through GND Pin 40mA Operating Temperature Range -40°C to +85°C Junction Temperature +150°C Storage Temperature Range -40°C to +85°C Soldering Temperature See IPC/JEDEC J-STD-020

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device.

ELECTRICAL CHARACTERISTICS

= -40°C to +85°C; see Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Power Supply

Supply Voltage V Supply Current (Note 5) I Standby Current I

DDS

(Note 2) 3.0 5.5 V VDD = 5.5V 1.5 mA VDD = 5.5V 1.5 µA

IO Pin General Data

1-Wire Pullup Voltage (Note 2)

1-Wire Pullup Resistance R

PUP

Local power 3.0 V Parasite power 3.0 5.5

(Notes 2, 3) Input Capacitance CIO (Notes 4, 5) 1000 pF Input Load Current I High-to-Low Switching

Threshold 2, 8)

Low-to-High Switching Threshold (Notes 5, 6, 9) Switching Hysteresis (Notes 5, 6, 10) Output Low Voltage (Note 11)

Recovery Time (Notes 2, 12)

(Notes 5, 13) (Notes 2, 14)

REC

REH

SLOT

IO pin at V

0.1 1.5 µA

PUP

(Notes 5, 6, 7) 0.46

Parasite powered 0.5 Input Low Voltage (Notes

VDD powered (Note 5) 0.7

Parasite power 1.0

Parasite power 0.21 1.7 V

At 4mA 0.4 V

Standard speed, R

Overdrive speed, R

= 2.2kΩ

PUP

= 2.2kΩ Overdrive speed, directly prior to reset pulse; R

= 2.2kΩ

PUP

Standard speed 0.5 5.0 Rising-Edge Hold-Off Time Overdrive speed Not applicable (0) Standard speed 65 Timeslot Duration Overdrive speed 8

IO Pin, 1-Wire Reset, Presence Detect Cycle

Reset Low Time (Note 2) t

Time (Notes 5, 15) Time Time (Notes 2,16)

RSTL

PDH

FPD

PDL

MSP

Standard speed 480 640 Overdrive speed 48 80 Standard speed 15 60 Presence-Detect High Overdrive speed 2 6 Standard speed 1.125 8.1 Presence-Detect Fall Time Overdrive speed 0 1.3 Standard speed 60 240 Presence-Detect Low Overdrive speed 8 24 Standard speed 68.1 75 Presence-Detect Sample Overdrive speed 7.3 10

0.3 2.2

PUP

1.9V

kΩ

V V

PUP

1.1V

5 2

µs

µs µs

µs µs µs µs µs

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DS28EA00 1-Wire Digital Thermometer with Sequence Detect and PIO

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

IO Pin, 1-Wire Write

(Notes 2, 17) (Notes 2, 17)

IO Pin, 1-Wire Read

Read Low Time (Notes 2, 18)

Read Sample Time (Notes 2, 18)

PIO Pins

Input Low Voltage V Input High Voltage (Note 2) Input Load Current (Note 19) Output Low Voltage (Note 11) Chain-on Pullup Impedance

EEPROM

Programming Current I Programming Time t

durance) (Notes 22, 23) Data Retention (Notes 24, 25)

W0L

W1L

MSR

ILP

IHP

OLP

PROG PROG

Standard speed 60 120 Write-0 Low Time Overdrive speed 6 16 Standard speed 5 15 Write-1 Low Time Overdrive speed 1 2

Standard speed Overdrive speed Standard speed Overdrive speed

(Note 2) 0.3 V VX = max(V

, VDD) Vx-1.6

PUP

Pin at GND -1.1 At 4mA 0.4 V

(Note 5) 20 40 60

(Notes 5, 20) 1.5 mA (Note 21) 10 ms At +25°C 200k Write/Erase Cycles (En-

-40°C to +85°C 50k

At +85°C (worst case) 10 years

µs µs

5 1

+ δ

15 - δ

2 - δ 15 2

µs

µA

kΩ

—

Temperature Converter Conversion Current I

CONV

(Notes 5, 20) 1.5 mA

12-bit resolution (1/16°C) 750 Conversion Time (Note 26)

CONV

11-bit resolution (1/8°C) 375

10-bit resolution (1/4°C) 187.5

9-bit resolution (1/2°C) 93.75 Conversion Error Converter Drift

Δϑ

-10°C to +85°C -0.5 +0.5

below -10°C (Note 5) -0.5 +2.0

(Note 27)

-0.2

+0.2 °C

°C

Note 1: Specifications at TA = -40°C are guaranteed by design only and not production-tested. Note 2: System requirement. Note 3: Maximum allowable pullup resistance is a function of the number of 1-Wire devices in the system and 1-Wire recovery times. The

Note 4: Value is 25pF max. with local power. Maximum value represents the internal parasite capacitance when V Note 5: Guaranteed by design, characterization, and/or simulation only. Not production tested.

Note 6: V

Note 7: Voltage below which, during a falling edge on IO, a logic '0' is detected. Note 8: The voltage on IO needs to be less than or equal to V Note 9: Voltage above which, during a rising edge on IO, a logic '1' is detected. Note 10: After V Note 11: The I-V characteristic is linear for voltages less than 1V. Note 12: Applies to a single parasitically powered DS28EA00 attached to a 1-Wire line. These values also apply to networks of multiple

Note 13: The earliest recognition of a negative edge is possible at t Note 14: Defines maximum possible bit rate. Equal to 1/(t Note 15: Interval during the negative edge on IO at the beginning of a Presence-Detect pulse between the time at which the voltage is

Note 16: Interval after t Note 17:

specified value here applies to parasitically powered systems with only one device and with the minimum 1-Wire recovery times. For more heavily loaded systems, local power or an active pullup such as that found in the DS2482-x00, DS2480B, or DS2490 may be required. If longer t

= 2.2kΩ, 2.5µs after V

PUP

, VTH, and V

are a function of the internal supply voltage, which is itself a function VDD, V

has been applied the parasite capacitance will not affect normal communications.

PUP

capacitive loading on IO. Lower V

, and VHY.

is crossed during a rising edge on IO, the voltage on IO has to drop by at least VHY to be detected as logic '0'.

is used, higher R

REC

, V

, higher R

PUP

values may be tolerable.

PUP

, shorter t

PUP

at all times the master drives the line to a logic '0'.

ILMAX

, and heavier capacitive loading all lead to lower values of VTL,

REC

PUP

, R

, 1-Wire timing, and

PUP

is first applied. If

DS28EA00 with local supply.

after VTH has been reached on the preceding rising edge.

REH

+ t

W0L(min)

80% of V limit is t

and the time at which the voltage is 20% of V

PUP

during which a bus master is guaranteed to sample a logic '0' on IO if there is a DS28EA00 present. Minimum

RSTL

PDH(max)

+ t

; maximum limit is t

FPD(max)

PDH(min)

+ t

PDL(min)

ε in Figure 14 represents the time required for the pullup circuitry to pull the voltage on IO up from V duration for the master to pull the line low is t

W1Lmax

+ tF - ε and t

REC(min)

PUP

+ tF - ε respectively.

W0Lmax

to VTH. The actual maximum

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DS28EA00 1-Wire Digital Thermometer with Sequence Detect and PIO

Note 18: Note 19: This load current is caused by the internal weak pullup, which asserts a logic '1' to the PIOB and PIOA pins. The logical state of Note 20: Current drawn from IO during EEPROM programming or temperature conversion interval in parasite powered mode. The pullup

Note 21: The t

Note 22: Write-cycle endurance is degraded as T Note 23: Not 100% production-tested; guaranteed by reliability monitor sampling. Note 24: Data retention is degraded as T Note 25: Guaranteed by 100% production test at elevated temperature for a shorter time; equivalence of this production test to data sheet

Note 26: The t

Note 27: Drift data is preliminary and based on a 1000-hour stress test performed on another device with comparable design and

δ in Figure 14 represents the time required for the pullup circuitry to pull the voltage on IO up from V of the bus master. The actual maximum duration for the master to pull the line low is t

PIOB must not change during the execution of the Conditional Read ROM command. circuit on IO during the programming or temperature conversion interval should be such that the voltage at IO is greater than or

equal to V programming or temperature conversions may need to be added. The bypass must be activated within 10µs from the beginning of the t

PROG

Scratchpad sequence. Interval ends once the device's self-timed EEPROM programming cycle is complete and the current drawn by the device has returned from I

limit at operating temperature range is established by reliability testing.

CONV

Temperature sequence. Interval ends once the device's self-timed temperature conversion cycle is complete and the current drawn by the device has returned from I

fabricated in the same manufacturing process. This test was performed at greater than +85°C with V drift results for this device are pending the completion of a new 1000-hour stress test.

. If V

PUP(min)

or t

interval begins t

PUP

interval, respectively.

CONV

in the system is close to V

after the trailing rising edge on IO for the last time slot of the command byte for a valid Copy

REHmax

to IL (parasite power) or I

PROG

increases.

after the trailing rising edge on IO for the last time slot of the command byte for a valid Convert

REHmax

to IL (parasite power) or I

CONV

then a low impedance bypass of R

PUP(min)

(local power).

DDS

(local power).

DDS

RLmax

+ tF

PUP

to the input high threshold

, which can be activated during

= 5.5V. Confirmed thermal

PIN DESCRIPTION

PIN NAME FUNCTION

1 IO 4 GND

2, 3, 5

7 8

N.C. No Connection

PIOA

(DONE\)

PIOB (EN\)

Power Supply Pin. Must be tied to GND for operation in parasite power mode.

1-Wire Bus Interface and Parasitic Power Supply. Open-drain, requires external pullup resistor. Ground Supply

Open-Drain PIOA Channel and Chain Output. For sequence detection, PIOA must be connected to PIOB of the next device in the chain; leave open or tie to GND for the last device in the chain. Open-Drain PIOB Channel and Chain Input. For sequence detection, PIOB of the first device in the chain must be tied to GND.

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DS28EA00 1-Wire Digital Thermometer with Sequence Detect and PIO

(

(ON\

)

OVERVIEW

The block diagram in Figure 1 shows the relationships between the major function blocks of the DS28EA00. The device has three main data components: 1) 64-bit Registration Number, 2) 64-bit scratchpad, and 3) alarm and configuration registers. The 1-Wire ROM Function control unit processes the ROM function commands that allow the device to function in a networked environment. The device function control unit implements the device-specific control functions, such as read/write, temperature conversion, setting the chain state for sequence detection, and PIO access. The CRC generator assists the master verifying data integrity when reading temperatures and memory data. In the sequence detect process, PIOB functions as an input, while PIOA provides the connection to the next device. The power supply sensor allows the master to remotely read whether the DS28EA00 has local power available.

Figure 2 shows the hierarchical structure of the 1-Wire protocol. The bus master must first provide one of the eight ROM function commands: 1) Read ROM, 2) Match ROM, 3) Search ROM, 4) Conditional (“Alarm”) Search ROM,

5) Conditional Read ROM, 6) Skip ROM, 7) Overdrive-Skip ROM or 8) Overdrive-Match ROM. Upon completion of an Overdrive ROM command byte executed at standard speed, the device enters Overdrive mode, where all subsequent communication occurs at a higher speed. The protocol required for these ROM function commands is described in Figure 12. After a ROM function command is successfully executed, the device-specific control functions become accessible and the master may provide any one of the nine available commands. The protocol for these control function commands is described in Figure 10. All data is read and written least significant bit

first.

Figure 1. DS28EA00 Block Diagram

Internal VDD

VDD

64-Bit

Registration #

PIOB

EN\)

8-Bit CRC Generator

Alarm and Config

Registers

Power Supply

Sensor

1-Wire ROM

Function Control

Device Function

Control

64-Bit Scratchpad

RCO

PIOA

DONE\)

Temperature

Sensor

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DS28EA00 1-Wire Digital Thermometer with Sequence Detect and PIO

64-BIT REGISTRATION NUMBER

Each DS28EA00 contains a unique Registration Number that is 64 bits long. The first 8 bits are a 1-Wire family code. The next 48 bits are a unique serial number. The last 8 bits are a CRC of the first 56 bits. See Figure 3 for details. The 1-Wire CRC is generated using a polynomial generator consisting of a shift register and XOR gates as shown in Figure 4. The polynomial is X Redundancy Check (CRC) is available in Application Note 27.

The shift register bits are initialized to 0. Then starting with the least significant bit of the family code, one bit at a time is shifted in. After the 8th bit of the family code has been entered, then the 48-bit serial number is entered. After the last byte of the serial number has been entered, the shift register contains the CRC value. Shifting in the 8 bits of CRC returns the shift register to all 0s.

Figure 2. Hierachical Structure for 1-Wire Protocol

+ X5 + X4 + 1. Additional information about the Dallas 1-Wire Cyclic

DS28EA00

Command Level:

1-Wire ROM Function

Commands (see Figure 12)

Device-Specific

Control Function

Commands (see Figure 10)

Available Commands:

Read ROM Match ROM Search ROM Conditional Search

ROM

Conditional Read

ROM Skip ROM Overdrive Skip Overdrive Match

Write Scratchpad Read Scratchpad Copy Scratchpad

Convert Temperature Read Power Mode

Recall EEPROM PIO Access Read

PIO Access Write Chain

Data Field Affected:

64-bit Reg. # 64-bit Reg. # 64-bit Reg. # 64-bit Reg. #, Temperature Alarm

Registers, Scratchpad

64-bit Reg. #, PIOB pin state, Chain

state (none) 64-bit Reg. #, OD-Flag 64-bit Reg. #, OD-Flag

Scratchpad Scratchpad Temperature Alarm and Configuration

Registers Scratchpad, Temperature Alarm

Registers V

pin voltage

Scratchpad, Temperature Alarm and

Configuration Registers PIO pins PIO pins Chain state, PIOA pin state

Figure 3. 64-Bit Registration Number

MSB LSB

8-Bit

CRC Code

MSB LSB MSB LSB MSB LSB

48-Bit Serial Number

8-Bit Family

Code (42h)

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DS28EA00 1-Wire Digital Thermometer with Sequence Detect and PIO

Figure 4. 1-Wire CRC Generator

Polynomial = X8 + X5 + X4 + 1

STAGE

INPUT DATA

STAGE

Memory Description

The memory of the DS28EA00 is shown in Figure 5. It consists of an 8-byte scratchpad and 3 bytes of backup EEPROM. The first two bytes form the temperature readout register, which is updated after a temperature conversion and is read-only. The next 3 bytes are user-writeable; they contain the Temperature High (TH) and the Temperature Low (TL) alarm register and a configuration register. The remaining 3 bytes are “reserved”. They power up with constant data and cannot be written by the user. The TH, TL, and configuration register data in the scratchpad control the resolution of a temperature conversion and decide whether a temperature is considered as “alarming”. TH, TL, and configuration can be copied to the EEPROM to become nonvolatile (NV). The scratchpad is automatically loaded with EEPROM data when the DS28EA00 powers up.

Figure 5. Memory Map

BYTE

ADDRESS

0 Temperature LSB (50h) N/A 1 Temperature MSB (05h) N/A

SCRATCHPAD (POWER-UP STATE) BACKUP EEPROM

2 TH Register or User Byte 1* <--------> TH Register or User Byte 1 3 TL Register or User Byte 2* <--------> TL Register or User Byte 2 4 Configuration Register* <--------> Configuration Register 5 Reserved (FFh) N/A 6 Reserved (0Ch) N/A 7 Reserved (10h) N/A

*Power-up state depends on value(s) stored in EEPROM.

Temperature Readout Register

ADDR bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

0 23 2

1 S S S S S 26 2

-1

-2

-3

-4 4

LS Byte

MS Byte

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DS28EA00 1-Wire Digital Thermometer with Sequence Detect and PIO The temperature reading is in °C using a 16-bit sign-extended two’s complement format. Table 1 shows examples

of temperature and the corresponding data for 12-bit resolution. With two’s complement, the sign bit is set if the value is negative. If the device is configured for 12-bit resolution, all bits in the LS byte are valid; for a reduced resolution, bit 0 (11 bit mode), bits 0 to 1 (10 bit mode), and bits 0 to 2 (9 bit mode) are undefined.

Table 1. Temperature/Data Relationship

TEMPERATURE

DIGITAL OUTPUT

(BINARY)

DIGITAL OUTPUT

(HEX)

+85°C* 0000 0101 0101 0000 0550h

+25.0625°C 0000 0001 1001 0001 0191h

+10.125°C 0000 0000 1010 0010 00A2h

+0.5°C 0000 0000 0000 1000 0008h

0°C 0000 0000 0000 0000 0000h

-0.5°C 1111 1111 1111 1000 FFF8h

-10.125°C 1111 1111 0101 1110 FF5Eh

-25.0625°C 1111 1110 0110 1111 FE6Fh

-40°C 1111 1101 1000 0000 FD80h

*The power-on reset value of the temperature readout register is +85°C.

Temperature Alarm Registers

ADDR bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

2 S 26 2 3 S 26 2

0 0

High Alarm (TH)

Low Alarm (TL)

The result of a temperature conversion is automatically compared to the values in the alarm registers to determine whether an alarm condition exists. Alarm thresholds are represented as two’s complement number. With 8 bits available for sign and value, alarm thresholds can be set in increments of 1°C. An alarm condition exists if a temperature conversion results in a value that is either higher than or equal to the value stored in the TH register or lower than or equal to the value stored in the TL register. If a temperature alarm condition exists, the device will respond to the Conditional Search command. The alarm condition is cleared if a subsequent temperature conversion results in a temperature reading within the boundaries defined by th e data in the TH and TL registers.

Configuration Register

ADDR b7 b6 b5 b4 b3 b2 b1 b0

4 0 R1 R0 1 1 1 1 1

The functional assignments of the individual bits are explained in the table below. Bits 0 to 4 and bit 7 have no function; they cannot be changed by the user. As a factory default, the device operates in 12-bit resolution.

BIT DESCRIPTION BIT(S) DEFINITION

R0, R1: Temperature Converter Resolution

b5, b6

These bits control the resolution of the temperature converter. The codes are as follows:

R1 R0

0 0 9 bits 0 1 10 bits 1 0 11 bits 1 1 12 bits

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DS28EA00 1-Wire Digital Thermometer with Sequence Detect and PIO

PIO Structure

Each PIO consists of an open-drain pulldown transistor and an input path to read the pin state. The transistor is controlled by the PIO Output Latch, as shown in Figure 6. The Device Function Control unit connects the PIOs logically to the 1-Wire interface. PIOA has a pullup path to internal V

to facilitate the sequence detect function

(see Figure 1) in conjunction with the Chain command; PIOB is truely an open-drain structure. The power-on default state of the PIO output transistors is off; high-impedance on-chip resistors (not shown in the graphic) pull the PIO pins to internal V

Figure 6. PIO Simplified Logic Diagram

PIO Pin

State

PIO Output

Latch State.

PIO Pin

PIO Data

PIO Clock

CLOCK

PIO Output Latch

Chain Function

The chain function is a feature that allows the 1-Wire master to discover the physical sequence of devices that are wired as a linear network (“chain”). This is particularly convenient for devices that are installed at equal spacing along a long cable, e.g., to measure temperatures at different locations inside a storage tower or tank. Without chain function, the master needs a lookup table to correlate registration number to the physical location.

The chain function requires two pins, an input (EN\) to enable a device to respond during the discovery and an output (DONE\) to inform the next device in the chain that the discovery of its neighbor is done. The two general purpose ports of the DS28EA00 are re-used for the chain function. PIOB functions as EN\ input and PIOA generates the DONE\ signal, which is connected to the EN\ input of the next device, as shown in the typical operating circuit on page 1. The EN\ input of the first device in the chain needs to be hardwired to GND or logic ‘0’ must be applied for the duration of the sequence discovery process. Besides the two pins, the sequence discovery relies on the Conditional Read ROM command.

For the chain function and normal PIO operation to coexist, the DS28EA00 distinguishes three chain states, OFF, ON, and DONE. The transition from one chain state to another is controlled through the Chain command. Table 2 summarizes the chain states and the specific behavior of the PIO pins.

Table 2. Chain States

CHAIN STATE

DEVICE BEHAVIOR

PIOB (EN\) PIOA (DONE\) Conditional Read ROM

OFF (default)

DONE

PIO (high impedance)

EN\ input Pullup on Recognized if EN\ is ‘0’ No function

PIO (high impedance)

Pulldown on (DO\ logic ‘0’)

Not recognized

The power-on default chain state is OFF, where PIOA and PIOB are solely controlled through the PIO Access Read and Write commands. In the chain ON state PIOA is pulled high to the device’s internal V

supply through a

~40kΩ resistor, applying a logic ‘1’ to the PIOB (EN\) pin of the next device. Only in the ON state does a DS28EA00 respond to the Conditional Read ROM command, provided its EN\ is at logic ‘0’. After a device’s ROM

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