Allen-Bradley FLEX I/O 1794-ID2 User manual

User
Manual
FLEX I/O 2 Input
Incremental
Encoder Module
(Cat. No. 1794-ID2)
Allen-Bradley
Allen-Bradley Motors

Because of the variety of uses for the products described in this
publication, those responsible for the application and use of this control
equipment must satisfy themselves that all necessary steps have been
taken to assure that each application and use meets all performance and
safety requirements, including any applicable laws, regulations, codes
and standards.
The illustrations, charts, sample programs and layout examples shown in
this guide are intended solely for example. Since there are many
variables and requirements associated with any particular installation,
Allen-Bradley does not assume responsibility or liability (to include
intellectual property liability) for actual use based upon the examples
shown in this publication.
Allen-Bradley publication SGI–1.1, “Safety Guidelines For The
Application, Installation and Maintenance of Solid State Control”
(available from your local Allen-Bradley office) describes some
important differences between solid-state equipment and
electromechanical devices which should be taken into consideration
when applying products such as those described in this publication.
Reproduction of the contents of this copyrighted publication, in whole or
in part, without written permission of Allen–Bradley Company, Inc.
is prohibited.
Throughout this manual we make notes to alert you to possible injury to
people or damage to equipment under specific circumstances.
!ATTENTION: Identifies information about practices or
circumstances that can lead to personal injury or death,
property damage, or economic loss.
Attention helps you:
•identify a hazard
•avoid the hazard
•recognize the consequences
Important: Identifies information that is especially important for
successful application and understanding of the product.
Important: We recommend you frequently backup your application
programs on appropriate storage medium to avoid possible
data loss.
DeviceNet, DeviceNetManager, and RediSTATION are trademarks of Allen-Bradley Company, Inc.
PLC, PLC–2, PLC–3, and PLC–5 are registered trademarks of Allen-Bradley Company, Inc.
Windows is a trademark of Microsoft.
Microsoft is a registered trademark of Microsoft
IBM is a registered trademark of International Business Machines, Incorporated.
All other brand and product names are trademarks or registered trademarks of their respective companies.
Important User Information


Publication 1794-6.5.15 – December 1998

This manual shows you how to use your FLEX I/O pulse counter
module with Allen-Bradley programmable controllers. The manual
helps you install, program and troubleshoot your module.
You must be able to program and operate an Allen-Bradley
programmable controller to make efficient use of your FLEX I/O
module. In particular, you must know how to program block
transfers.
We assume that you know how to do this in this manual. If you do
not, refer to the appropriate programming and operations manual
before you attempt to program your modules.
In this manual, we refer to:
–the pulse counter module as the “input module”
–the Programmable Controller as the “controller”
This manual is divided into eight chapters. The following chart lists
each chapter with its corresponding title and a brief overview of the
topics covered in that chapter.
Chapter Title Contents
1Overview of FLEX I/O and the
Pulse Counter Module Describes FLEX I/O pulse counter modules, features, and how they function
2How to Install Your Pulse Counter
Module How to install and wire the module
3Module Programming Explains block transfer programming, sample programs
4Writing Configuration to and
Reading Status From with a
Remote I/O Adapter
Explains how to configure your modules and read status
information from your modules when using a remote I/O
adapter
5How Communication Takes Place
and I/O Image Table Mapping
with the DeviceNet Adapter
Explains how you communicate with your modules, and
how the I/O image is mapped when using a DeviceNet
adapter
6Input, Output and Configuration
files for Analog Modules using
ControlNet
Explains how you communicate with your modules, and
how the I/O and configuration files are mapped when using
a ControlNet adapter
7Calibrating Your Pulse Counter
Module How to calibrate the module.
8Troubleshoot Your Pulse Counter
Module How to use the indicators to troubleshoot your module.
Purpose of this Manual
Audience
Vocabulary
Manual Organization
Allen-Bradley Motors

Using This ManualP–2
Publication 1794-6.5.15 – December 1998
Appendix Title Contents
ASpecifications Specifications for the pulse counter module
We use these conventions in this manual:
In this manual, we show: Like this:
that there is more information about a topic
in another chapter in this manual
that there is more information about the
topic in another manual More
For additional information on FLEX I/O systems and modules, refer
to the following documents:
Catalo
Volta e
Descr pt on
Publications
Catalo
g
Number Voltage Description Installation
Instructions User Manual
1794 1794 FLEX I/O Product Data 1794-2.1
1794-ACN 24V dc ControlNet Adapter 1794-5.8
1794-ACNR 24V dc Redundant Media ControlNet Adapter 1794-5.18
1794-ACN15 24V dc ControlNet Adapter 1794-5.47
1794-ACNR15 24V dc Redundant Media ControlNet Adapter 1794-5.48
1794-ADN 24V dc DeviceNet Adapter 1794-5.14 1794-6.5.5
1794-ASB/C 24V dc Remote I/O Adapter 1794-5.50 1794-6.5.9
1794-ASB2/B 24V dc 2-Slot Remote I/O Adapter 1794-5.44 1794-6.5.13
1794-APB 24V dc Profibus Adapter 1794-5.40 1794-6.5.6
1794-IB8 24V dc 8 Sink Input Module 1794-5.30
1794-OB8 24V dc 8 Source Output Module 1794-5.31
1794-IB16 24V dc 16 Sink Input Module 1794-5.4
1794-OB16 24V dc 16 Source Output Module 1794-5.3
1794-IV16 24V dc 16 Source Input Module 1794-5.28
1794-OV16 24V dc 16 Sink Output Module 1794-5.29
1794-OB8EP 24V dc 8 Electronically Fused Output Module 1794-5.20
1794-IB8S 24V dc Sensor Input Module 1794-5.7
1794-IB10XOB6 24V dc 10 Input/6 Output Module 1794-5.24
1794-IE8 24V dc Selectable Analog 8 Input Module 1794-5.6
1794-6.5.2
1794-OE4 24V dc Selectable Analog 4 Output Module 1794-5.5
1794-6.5.2
Table continued on next page
Conventions
For Additional Information

Using This Manual P–3
Publication 1794-6.5.15 – December 1998
Publications
DescriptionVoltage
Catalog
Number User
Manual
Installation
Instructions
DescriptionVoltage
Catalog
Number
1794-IE4XOE2 24V dc 4 Input/2 Output Analog Module 1794-5.15 1794-6.5.2
1794-OF4 24V dc 4 Output Isolated Analog Module 1794-5.37
1794-IF4 24V dc 4 Input Isolated Analog Module 1794-5.38 1794-6.5.8
1794-IF2XOF2 24V dc 2 Input/2 Output Isolated Analog Module 1794-5.39
1794-IR8 24V dc 8 RTD Input Analog Module 1794-5.22 1794-6.5.4
1794-IT8 24V dc 8 Thermocouple Input Module 1794-5.21 1794-6.5.7
1794-IRT8 24V dc 8 Thermocouple/RTD Input Module 1794-5.50 1794-6.5.12
1794-IJ2 24V dc 2 Frequency Input Module 1794-5.49 1794-6.5.11
1794-IA8 120V ac 8 Input Module 1794-5.9
1794-OA8 120V ac Output Module 1794-5.10
1794-TB2
1794-TB3 2-wire Terminal Base 3-wire Terminal Base 1794-5.2
1794-TBN Terminal Base Unit 1794-5.16
1794-TBNF Fused Terminal Base Unit 1794-5.17
1794-TB3T Temperature Terminal Base Unit 1794-5.41
1794-TB3S Spring Clamp Terminal Base Unit 1794-5.42
1794-TB3TS Spring Clamp Temperature Base Unit 1794-5.43
1794-TB3G Terminal Base Unit 1794-5.51
1794-TB3GS Spring Clamp Terminal Base Unit 1794-5.59
1794-CE1, -CE3 Extender Cables 1794-5.12
1794-NM1 Mounting Kit 1794-2.13
1794-PS1 24V dc Power Supply 1794-5.35
This preface gave you information on how to use this manual
efficiently. The next chapter introduces you to the frequency
module.
Summary
Allen-Bradley Motors

Using This ManualP–4
Publication 1794-6.5.15 – December 1998

Publication 1794-6.5.15 – December 1998
Chapter 1
What This Chapter Contains 1–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
How Y
ou Use the Incremental Encoder Module 1–1. . . . . . . . . . . . . . .
What
the Incremental Encoder Module Does 1–2. . . . . . . . . . . . . . . . .
Typical
Applications 1–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input
Capabilities 1–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
How
the Incremental Encoder Operates 1–4. . . . . . . . . . . . . . . . . . . . .
Variables 1–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Start
Counting 1–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Selecting
the incremental encoder and up/down counting 1–4. . . . . .
Up/Down
Counting Controlled by B Input 1–5. . . . . . . . . . . . . . . . . .
Up/Down
Counting using Pulses at Inputs A and B 1–5. . . . . . . . . . .
Count Pulses from Incremental Encoders 1–6. . . . . . . . . . . . . . . . .
Preset
Function 1–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gate
Function 1–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Store
Function 1–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Limitation
Function 1–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter Summary 1–9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 2
What This Chapter Contains 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Before Y
ou Install Y our Input Module 2–1. . . . . . . . . . . . . . . . . . . . . . .
European
Union Directive Compliance 2–1. . . . . . . . . . . . . . . . . . . . . .
EMC Directive 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low V
oltage Directive 2–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Requirements 2–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wiring
the T erminal Base Units (1794-TB3G shown) 2–3. . . . . . . .
Installing
the Module 2–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mounting
the T erminal Base Unit on a DIN Rail 2–4. . . . . . . . . . . . .
Panel/Wall
Mounting 2–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mounting
the Incremental Encoder Module on the T erminal
Base Unit 2–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Connecting
Wiring for Y our incremental encoder Module 2–9. . . . . . . . .
Wiring
to a 1794-TBN or -TBNF T erminal Base Unit 2–11. . . . . . . . . .
Wiring
connections for the 1794–ID2 incremental encoder Module 2–12
Example of Pulse T ransmitter Wiring 2–13. . . . . . . . . . . . . . . . . . . . .
Example
of Incremental Encoder Wiring 2–13. . . . . . . . . . . . . . . . . .
Module
Indicators 2–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter Summary 2–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table of Contents
Overview of the Incremental
Encoder Module
How to Install Your
Incremental Encoder Module
Allen-Bradley Motors

Table of Contentsii
Publication 1794-6.5.15 – December 1998
Chapter 3
What This Chapter Contains 3–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Enter Block Transfer Instructions 3–1. . . . . . . . . . . . . . . . . . . . . . . . . .
PLC-2 Family Processor 3–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLC-5 Family Processor 3–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SLC-5 Programming 3–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter Summary 3–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 4
What This Chapter Contains 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ConfiguringY
our Incremental Encoder Module 4–1. . . . . . . . . . . . . . . .
Reading Data From Y
our Module 4–2. . . . . . . . . . . . . . . . . . . . . . . . .
Mapping
Data for the Module 4–2. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Incremental
Encoder Module (1794-ID2) Image T able Mapping 4–2. .
Block
T ransfer Read W ord Assignments for the Incremental Encoder
Module (1794-ID2) 4–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bit/Word
Definitions for Block T ransfer Read W ords for the
Incremental Encoder Module 4–3. . . . . . . . . . . . . . . . . . . . . .
Block
T ransfer W rite W ord Assignments for the Incremental Encoder
Module 4–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bit/Word
Definitions for the Block T ransfer W rite W ords for the
Incremental Encoder Module 4–5. . . . . . . . . . . . . . . . . . . . . .
Chapter Summary 4–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 5
What This Chapter Contains 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
About DeviceNetManager Software 5–1. . . . . . . . . . . . . . . . . . . . . . . .
Polled I/O Structure 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adapter
Input Status W ord 5–2. . . . . . . . . . . . . . . . . . . . . . . . . . . .
System
Throughput 5–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mapping
Data into the Image T able 5–3. . . . . . . . . . . . . . . . . . . . . . . .
Incremental
Encoder Module (1794-ID2) Image T able Mapping 5–3. .
Block
T ransfer Read W ord Assignments for the Incremental Encoder
Module (1794-ID2) 5–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Block
T ransfer W rite W ord Assignments for the Incremental Encoder
Module (1794-ID2) 5–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bit/Word
Definitions for the incremental encoder Module
(1794–ID2) 5–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Defaults 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Programming Your
Incremental Encoder Module
Writing Configuration to and
Reading Status from Your
Module with a Remote I/O
Adapter
How Communication Takes
Place and I/O Image Table
Mapping with the DeviceNet
Adapter

Table of Contents iii
Publication 1794-6.5.15 – December 1998
Chapter 6
Chapter Objectives 6–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
About
the ControlNet Adapter 6–1. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Scheduled
Data-T ransfer 6–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unscheduled
Data-T ransfer 6–2. . . . . . . . . . . . . . . . . . . . . . . . . . .
Module
I/O Mapping 6–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O
Structure 6–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adapter
Input Status W ord 6–3. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Safe
State Data 6–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Device Actions 6–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Communication
Fault Behavior 6–5. . . . . . . . . . . . . . . . . . . . . . . . .
Idle
State Behavior 6–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input
Data Behavior upon Module Removal 6–5. . . . . . . . . . . . . . . .
Incremental
Encoder Module (1794-ID2) Image T able Mapping 6–6. .
Bit/Word
Definitions for Block T ransfer Read W ords for the
Pulse Counter Module 6–6. . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 7
Chapter Objective 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CalibratingY
our Module 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Calibration
Method 1 7–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Calibration
Method 2 7–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 8
What This Chapter Contains 8–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Status
Indicators 8–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
What’s Next 8–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Appendix A
Specifications A–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input, Output and
Configuration Files for
Analog Modules when used
with ControlNet
Calibrating Your Incremental
Encoder Module
Troubleshoot the
Incremental Encoder Module
Specifications
Allen-Bradley Motors

Table of Contentsiv
Publication 1794-6.5.15 – December 1998

Chapter 1
Publication 1794-6.5.15 – December 1998


Read this chapter to familiarize yourself with the 1794–ID2 module.
For information on See page
How You Use the incremental encoder Module . . . . . . . . . . . 1–1
What the incremental encoder Module Does . . . . . . . . . . . . . 1–2
Input Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–3
How the incremental encoder Operates . . . . . . . . . . . . . . . . . 1–4
The 1794–ID2 module is an intelligent I/O module designed to
perform high speed pulse counting. The module provides:
•2 pulse transmitter interfaces, each with 4 optocoupled inputs
Each input has + and – inputs for connection to transmitters with
complementary and noncomplementary signals.
The pulse inputs can accept frequencies up to 100KHz. The module
accepts and returns binary data.
The module’s primary use is accurate, high-speed counting of pulse
from pulse transmitters or incremental encoders with 1 or 2 pulse
trains. This includes quantity counting, positioning and speed
calculations.
The module has 2 up/down counters, each individually
programmable. The number of edges to be counted can be multiplied
by 1, 2 or 4 (x1, x2, x4). Pulse transmitters can be complementary or
noncomplementary.
What This Chapter
Contains
How You Use the
Incremental Encoder
Module
Allen-Bradley Motors

1–2 Overview of the Incremental Encoder Module
Publication 1794-6.5.15 – December 1998
+A+
A–
B+
B–
Z+
Z–
G+
G–
Preset Register
Counter Register
Latch Register
Control Word
Signal Register
Logic
+A+
A–
B+
B–
Z+
Z–
G+
G–
Preset Register
Counter Register
Latch Register
Control Word
Signal Register
Logic
Gavanically Isolated
dc/dc Converter
Internal +5V dc 12–24V dc
0V
Serial Bus
Bus Interface
Optocouplers
The incremental encoder module performs high-speed scaling
calculation operations for various industrial applications. The
module interfaces with a FLEX family adapter which then
communicates with a programmable controller processor that has
block-transfer capability and external I/O devices.
The adapter/power supply transfers data to the module (block
transfer write) and from the module (block transfer read) using BTW
and BTR instructions in your ladder diagram program. These
instructions let the adapter read input values and status from the
module, and let you write output values and configure the module’s
mode of operation. The following illustration describes the
communication process.
What the Incremental
Encoder Module Does

1–3Overview of the Incremental Encoder Module
Publication 1794-6.5.15 – December 1998
ADAPTER
ACTIVE FAULT LOCAL
FAULT
24VDC
POWER SUPPLY
RIO ADAPTER
1794-ASB
Allen-Bradley
1
The adapter transfers your configuration data
to the module using a BTW.
Flexbus
External devices transmit
frequency signals to the module.
2
The module converts
frequency signals into integer
format and stores these values
until the adapter requests their
transfer.
3
Your ladder program instructs the
adapter to perform a BTR of the values
and stores them in a data table.
4
The adapter and module determine
that the transfer was made without error
and input values are within specified
range.
5
Your ladder program can use and/or move the data (if valid)
before it is written over by the transfer of new data in a
subsequent transfer.
6
Your ladder program performs BTWs to the module when you power
it up, and any time you wish to reconfigure the module.
7
OK
2 CH INCREMENTAL ENCODER
1
1794–ID2
Allen-Bradley
You can use the 1794–ID2 module in the power management,
automotive, food and beverage, and oil and gas industries for various
flow and/or turbine metering applications. Some sample
applications include:
•turbine shaft speed monitoring
•automotive paint booths
•brewery flow monitoring
•petrochemical flow and custody transfer
The incremental encoder module has 2 identical input channels.
Each of the input channels may accept these input signals:
•A+ and A–
•B+ and B–
•Z+ and Z–
•G+ and G–
The pulse inputs can accept frequencies up to 100KHz. The module
accepts and returns binary data.
Typical Applications
Input Capabilities
Allen-Bradley Motors

1–4 Overview of the Incremental Encoder Module
Publication 1794-6.5.15 – December 1998
The counter module handles up/down counting and detection of
selectable number of edges (X1, X2, X4) for incremental encoders
with 2 pulse trains, nominal 90oout of phase. The minimum stable
input condition is 2µs.The following paragraphs detail operation of
the incremental encoder module.
Each of the 2 counters has a 16–bit counter register, a preset register
and a latch register.
Variables
Communication between the counter module and the control system
uses variables accessible in the control system program. These
variables include:
•a counter register (Counter)
•a preset register (PresetValue)
•a latch register (LatchValue).
Signal registers and control words are used to set parameters for the
counter configuration. The control word sent to the incremental
encoder module can be read back to the control system, allowing
verification that one I/O scan been performed since the cycle has
been initiated.
Start Counting
The control bit CounterEnable enables counting. It must be set to 1
to enable counting and all other functions.
Selecting the Incremental Encoder and up/down counting
Depending on the incremental encoder, the module can be set in
different counter modes. The parameter is set using a 3 digit code in
write word 1 or 2 (depending on the channel) control word.
Mode Selection
Bit 02 01 00 Mode Selection bits
000Counting on positive (rising) edge of input signal A. (Up/dwn
counting determined by B.)
001Quadrature encoder X1
010Quadrature encoder X2
011Quadrature encoder X4
100Counting up on the positive edge of input signal A, and down
on positive edge of input signal B.
101No count function.
110No count function.
111No count function.
How the Incremental
Encoder Operates

1–5Overview of the Incremental Encoder Module
Publication 1794-6.5.15 – December 1998
Up/Down Counting Controlled by B Input
Pulse Counting (Mode 000)
12321
The positive edge of the pulses are counted at input A. If input B = 0,
the counter counts up; if B = 1, the counter counts down.
Input A
Input B 0
Counter Mode = 0 Counter Register
Logic
A
B = 0/1
Counter Value
Counting Up Counting Down
Up/Down
Up/Down
counting controlled by input B
Up/Down Counting using Pulses at Inputs A and B
10 2 1
The counter counts up on the positive edge of the pulses at input A,
and counts down on the positive edge of input B.
Input A
Input B 0
Counter Mode = 4 Counter Register
Logic
A
B
Counter Value
Up/Down
1
Up/Down Counting using pulses at the inputs of A and B
Pulse Counting Mode (100)
Allen-Bradley Motors

1–6 Overview of the Incremental Encoder Module
Publication 1794-6.5.15 – December 1998
Count Pulses from Incremental Encoders
If countermode = 1, 2 or 3, then 1, 2 or 4 edges of the pulse train will be counted. The count
direction (up/down) is determined by the phase dif ference of the input signals A and B.
Counter Mode = 1, 2 or 3
Counter Register
Logic
A
BUp/Down
Up/Down Counting using pulses at the inputs of A and B
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Input A
Input B
Counter Value Counting Up Counting Down
Example 1 – Counter Mode = 1 (x1)
0
13542
Input A
Input B
Counter Value Counting Up Counting Down
Example 2 – Counter Mode = 2 (x2)
02 4 3 1
15984
Input A
Input B
Counter Value Counting Up Counting Down
Example 3 – Counter Mode = 3 (x4)
03 7 6 248 5 12 6 7 3
Pulse Counting Mode (001, 010. 01 1)

1–7Overview of the Incremental Encoder Module
Publication 1794-6.5.15 – December 1998
Preset Function
Use the preset function to copy a value from the preset register to the
counter register.
Counter Register
Counter Register
Preset Register
Logic
PresetEnable = 1
Preset
Z =
Preset Register
PresetReached = 1
PresetReached = 1
Method
1
Method 2
The flag PresetReached is set when the counter register and the
preset register are equal (if the counter preset is reached, or if the
counter has been loaded with the preset value). This flag is reset on a
positive edge of PresetReset after the operation and can only be set
after at least one additional counting pulse.
Gate Function
Use the gate function to determine when counting starts and
stops.You can use this function to measure distance.
The parameter GateControl determines the gate function. The gate
signal is connected to input G. It is a 2–bit binary code in write word
1 or 2, bits 09 and 10
Word
1 or 2
Gate Control Function
1 or 2
Bits
09–10
Binary 10 09 Gate Control bits
09–10
0 0 0 No gate function on input G (Count is independent)
1 0 1 Counting only if G = 1 (active)
2 1 0 Counting only if G = 0 (inactive)
3 1 1 Calibration if G = 1 and all other conditions are
fulfilled (refer to Calibrating the Module, chapter ?).
Gate Control = 1
Counter Register
Logic
A
G = 1
The counter is counting if G = 1.
E
xample
Allen-Bradley Motors

1–8 Overview of the Incremental Encoder Module
Publication 1794-6.5.15 – December 1998
Store Function
Use the store function to copy the value in the counter register
(Counter) to the latch register (StoreValue).
The StoreControl parameter determines the store function. Execution
occurs on either the positive or negative edge of input signals G and
Z respectively (see table). The parameter is a 2–bit binary code in
write word 1 (bits 11 and 12)
Word
1 or 2
Bits
11–12
Binary 12 11 Store Control bits
1 or 2
11–12
0 0 0 Save the counter value on the positive edge of Z
(if Stored X = 0)
1 0 1 Save the counter value on the positive edge of G
(if Stored X = 0)
2 1 0 Save the counter value on the negative edge of G
(if Stored X = 0)
3 1 1 Save the counter value on both the positive edge
and negative edge of G (if Stored X = 0)
The parameter Stored must be reset (0). Stored is set (1) when the
operation is completed. Reset after the operation with StoreReset.
Store Control = 1 Counter Register
Logic
G
Stored = 0
The counter value is copied to the store register on the positive edge of input signal G.
E
xample
Store Register
Latched = 1
Limitation Function
If the control bit RangeLimited = 1, the counter counts up to the
preset value and restarts at 0. Counting down, the counter reaches the
preset value on the next pulse if the current counter value = 0.
RangeLimited = 0 corresponds to RangeLimited = 1 if the preset
value = FFFF in hex = 65535 in decimal.
The flag PresetReached is set when the counter is equal to the preset
value. Use PresetReset to reset the flag.

1–9Overview of the Incremental Encoder Module
Publication 1794-6.5.15 – December 1998
Value 0
Counter Register
Counter Register
Preset Register
Logic
RangeLimited = 1
RangeLimited = 1 Logic
Count
Up
pulse
(+)
Count Down pulse (–)
Counter = 0
Counter = PresetValue
Note: If the preset register value = 0, the counter retains the value 0.
In this chapter, you learned about the incremental encoder module,
block transfer communication, and details of how the module
functions. Now you can install the module.
Install the
ID2 Module

Chapter Summary
Allen-Bradley Motors

1–10 Overview of the Incremental Encoder Module
Publication 1794-6.5.15 – December 1998