Configuração modbus yokogawa

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2 23.09.2009

REMARKS

FINAL ISSUE -

-FOR APPROVAL FIRST ISSUE

REVISION HISTORY

DATE OF REVISIONREV.NO BRIEF DESCRIPTION OF REVISION SHEET NUMBERS REVISED

FOR INFORMATION

NAME CUSTOMER : TITLE : FUNCTIONAL DESIGN

PRD.RK

CHK. RS PROJECT :

APP. PVD

YOKOGAWA INDIA LIMITED

PETROQUIMICASUAPE PETROCHEMICAL CO. LTD PROJ DOC NO: AU2103-K06-006

PAGE NO : II/II

SPECIFICATION FOR SUB SYSTEM COMMUNICATION

DCS & ESD SYSTEMS FOR PQS PTA

YIL DOC NO: MP17-DS1-SCS

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FUNCTIONAL DESIGN SPECIFICATION FOR SUB-SYSTEM COMMUNICATION

Consultant: M/s AKER SOLUTIONS End-user: PETROQUIMICASUAPE CO. LTD

Proj Doc No : AU2103-K06-006 YIL Document No.: MP17-DS1-SCS

Job Name: DCS & ESD SYSTEMS FOR PQS

PTA PROJECT Revision: 2

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FUNCTIONAL DESIGN

SPECIFICATION FOR SUB SYSTEM COMMUNICATION

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CONTENTS

1 General ................................................................................................... 3 1.1 Introduction ............................................................................................................................ 3 1.2 Scope ..................................................................................................................................... 3 1.3 Structure ................................................................................................................................ 3 1.4 Definitions, Abbreviations and Terminology .......................................................................... 4

2 Subsystem Overview .............................................................................. 5

3 DCS Subsystem Communication: MODBUS – RTU .............................. 6 3.1 Philosophy ............................................................................................................................. 6 3.2 Communication Function ....................................................................................................... 8 3.2.1 Communication Function – Outline ........................................................................................ 8 3.2.2 Redundancy ......................................................................................................................... 11 3.3 DCS Communication Capacities ......................................................................................... 11 3.4 Communication Performance .............................................................................................. 12 3.5 Communication Interface ..................................................................................................... 12 3.6 Cable connection specification for ALR121 ......................................................................... 13 3.6.1 Cable Specifications for RS-422/RS-485 Communication Links ......................................... 15 3.7 Transmission specifications ................................................................................................. 15 3.8 CS3000: Setting items for ALR121 ...................................................................................... 17 3.9 Subsystem Addressing and Function Codes ....................................................................... 18 3.10 Time Synchronization With Subsystem ............................................................................... 19 3.11 Setting Items on Communication I/O Builder ....................................................................... 21 3.12 System Alarm Message ....................................................................................................... 23 3.12.1 System Alarm Messages ..................................................................................................... 23 3.12.2 Communication Error Codes ............................................................................................... 25 3.13 Subsystem I/O mapping ...................................................................................................... 27 3.13.1 I/O Mapping Principle .......................................................................................................... 27 3.13.2 Accessing Subsystem Data from a Function Block ............................................................. 28 3.13.3 Overview of Accessing Subsystem Data ............................................................................. 28 3.13.4 Access in case of Analog input from subsystem ................................................................. 29 3.13.5 Access in case of Analog output to the subsystem ............................................................. 30 3.13.6 Access in cases of discrete input and output to and from the subsystem ........................... 31

4 Sub-Systems used in the Project. ......................................................... 33

5 Sub-System Mapping Format ............................................................... 34

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1 General

1.1 Introduction

This section describes the basic specifications for communication with other sub-systems, via the ALR121 Communication Module using Modbus Protocol.

This section also describes a Simplified Redundant Function with Read / Write to be implemented in the CENTUM-VP, the hardware requirement, communication interface details, error codes and engineering methodology.

1.2 Scope

This document describes the Functional Design Specification for the DCS Communication with various third party sub-systems in the “DCS & ESD SYSTEMS FOR PQA PTA PROJECT “.

1.3 Structure

The document Structure is:

Chapter 1: General information on this specification including definitions and abbreviations used.

Chapter 2: Outlines the Subsystem overview and communication interface.

Chapter 3: Describes the MODBUS RTU protocol implementation, communication capacity and details the signal flow, exchange mechanism.

Chapter 4: Lists the subsystems in this project.

Chapter 5: Provides a format in which tags details are to be furnished by the subsystem vendor for mapping of subsystem into DCS.

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1.4 Definitions, Abbreviations and Terminology

AI Analog Input

AI/O Analog Input/Output

ALR121 Serial Communication Interface Module in DCS

AO Analog Output

DCS Process Control System

DI Digital Input

DI/O Digital Input/Output

DO Digital Output

ESB Bus Extended SB Bus (Internal Communication Bus) in a FCS

FCS Field Control Station

FIO Field Input/Output

HIS Human Interface Station

I/O Input/Output

IOP-/+ Input Low (open)/High (overshoot)

LAN Local Area Network

LED Light Emitting Diode

LSB Least Significant Bit

MAN Manual

MSB Most Significant Bit

MV Manipulated Value (Output Variable)

NU Node Unit

PLC Programmable Logic Controller

PV Process Variable

RTU Remote Termination Unit

SEBOL Sequence and Batch Oriented Language

SFC Sequence Function Chart

TBA To Be Assign

VNET/IP Yokogawa DCS Network

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2 Subsystem Overview

The DCS communication with the various Third party subsystems shall be realized as following.

SubsystemModbus-RTU

RS-485

Vnet/IP Bus 1

Vnet/IP Bus 2

Ethernet

Operator Station [HIS]

Controller [FCS]

Higher level System

For Monitoring / Control Applications

Subsystem communication: By Modbus – RTU protocol

The Subsystems, which require the Monitoring & Control operations from the DCS system, shall be based on MODBUS –RTU protocol & the communication links shall be RS485.

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3 DCS Subsystem Communication: MODBUS – RTU

The following sections describe the General Specification for the Subsystem communication implementation by using Modbus RTU protocol.

3.1 Philosophy

The Control System configuration involves communication with Sub-Systems.

Interface module ALR121 is to be housed in one of the node units (NU) in the Field Control Station (FCS). If a redundant communication required, the first (MASTER) communication module should be installed in an odd numbered slot, and it’s redundant (SLAVE) in the next contiguous even slot.

This communication link performs the following functions:

• Exchange of all necessary process data for monitoring and control (if applicable).

• Time Synchronization between DCS and sub-system (wherever applicable).

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ALR121

RS485 ModbusPLC

ModbusPLC

ModbusPLC

FCS

Note: All the subsystem communication interface shall be standardized to RS422/RS485 Modbus RTU interface. This is required to overcome the Cable length limitation posed by RS232C links.

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3.2 Communication Function

3.2.1 Communication Function – Outline

The Block Diagram below shows the communication I/O data flow for ALR121 communication module in CS 3000 DCS when interfaced with subsystems.

SUBSYSTEM ALR121 CommunicationPackage

Comm. I/O DataStorage

ControlFunctions

The Communication Package is a program downloaded to the ALR121 module; its main function is to convert the information to be exchanged with the subsystem in accordance with the Communication Protocol used.

Comm. I/O data storage area, also called the I/O image table, gathers the communication data and makes it available for control functions. In case of a redundant configuration, two ALR121 Modules will be required and an additional program to control the switching functions between the two communication modules.

The figure (Read Function & Write Function) shows configuration of Redundant Communication Function implemented in the FCS and ALR121 communication program using special software.

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1. Read Function

The two ALR121 cards will be executing asynchronously, accessing the sub-system. Sub-system data read by each ALR121 card will be stored in its own I/O image in the FCS. The redundant function monitors the condition of the two ALR121 cards and the communication. If the master side fails, the redundant function will copy the backup I/O image into the master I/O image of the FCS.

ALR121 ALR121

CONTROL SIDE(MASTER)

STAND-BYSIDE

Data OverWrite

SWITCH INSTRUMENT

SEQUENCE TABLE

CONTINOUS CONTROL INSTRUMENT

Read

REDUNDANTFUNCTION

SUB-SYSTEM

MASTER I/OIMAGE AREA

BACKUP I/OIMAGE AREA

Comm.Card

Comm.Card

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2. Write Function

Each function block must write the I/O image to the master side only which in turn writes to the sub-system through the ALR121 communication program. The I/O will be copied to the backup side when the master side fails. The Changes in I/O information are set to I/O image area via the redundant function.

CommCard

CommCard

ALR121 ALR121

CONTROLSIDE

STAND-BYSIDE

DataOverwrite

SWITCH INSTRUMENT

SEQUENCE TABLE

CONTINOUS CONTROL INSTRUMENT

Write

REDUNDANTFUNCTION

SUB-SYSTEM

Changinginformation

MASTER I/OIMAGE AREA

BACKUPI/OIMAGE AREA

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3.2.2 Redundancy

For a redundant link two ALR121 cards are used as control and stand-by respectively. In case of read communication, both cards will read data from the sub-system independently, but only control side data will be delivered.

In case of write communication, only the control side will communicate. Incase of malfunctioning, control switching will take place as follows:

Initially, the master ALR121 card is the controlling side, and the backup card is standby side.

1. When the master ALR121 card detects abnormal condition or sub-system communication

error occurs, and if the backup ALR121 card and sub-system communication is normal, switching will take place.

2. When both ports on the stand-by card are normal and the communication on the master card is abnormal.

3.3 DCS Communication Capacities

The capacity specific to Modbus when performing subsystem communication with a Modbus-RTU PLC is indicated below:

Item Capacity

No. Of ALR121 cards per FCS Max 16 nos. (8 Redundant)

Sub-system connectable per FCS 4 types (4 different Communication Protocols)

Amount of data handled by one ALR121 card Max 1000 words (16bits = 1 word)

No. Of Communication I/O data per FCS Max 4000 words

Number of DI/DO’s configurable per card Max 1000 tags

Number of DI/DO’s configurable per FCS Max 1000 tags

No of Words per transmission Max 125 Words (A I/O)

Max 8 Words (D I/O)

No. Of ports in one ALR121 card 2 (Same Protocol for both)

No. Of stations that can be handled by one port 30 Stations

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3.4 Communication Performance

The Communication performance over the MODBUS –RTU protocol is dependent on the following factors

a. No of words per transmission frame.

b. Subsystem Communication data shall be with contiguous addresses & packed in units of words, so as to minimize the number of data to be acquired and set by the FCS.

3.5 Communication Interface

The ALR121 are serial communication modules that are installed to the node unit for ESB bus (ANB10S, ANB10D).

• ALR121: 10 pole terminal block for two RS-422 or RS-485 ports (5 poles/port)

The following diagram indicates the external views of Serial communication modules.

LED Display Indications: • STATUS : This LED turns on (green

colour)when the self-diagnosis has been completed normally and the hardware is ready, otherwise it is turned off.

• ACT : When the module is operating normal, LED is ON(green colour) otherwise it is turned off.

• DX : This LED turns on(green colour) when module is configured for dual-redundant operation.

• SND-1 & 2: This LED turns on (green colour)during data transmission, otherwise it is turned off. The status is as per the Communication port basis.

• RCV-1 & 2: This LED turns on (green colour) during data reception, otherwise it is turned off. The status is as per the Communication port basis.

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3.6 Cable connection specification for ALR121

The following cable connection methodology shall be considered while using ALR121 cards as follows;

• RS-422: [Point- to –Point communication]: 4 wire connection

• RS-485: [Point to Point or Multipoint communication]: 2 wire connection

The following table shows the connector specification of the ALR121 card.

The ALR121 card can be either used for a 4-wire or 2-wire type of connection. The default connection type is 4-wire mode.

Cable connection when ALR121 is used with RS422 for Point-to-Point Communication [ 1:1 ], 4-wire connection is as follows,

ALR121 SUB-SYSTEM

SDA

SDB

RDA

RDB

SG

TX+

TX-

RX+

RX-

SG

120 120

120

Requirement of Termination resistance at the Sub-system end varies for each subsystem. Subsystem vendor to confirm.

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Cable connection when ALR121 is used with RS485 for Point-to-Point Communication [1:1 ], 2-wire connection is as follows,

ALR121 SUB-SYSTEM

SDA

SDB

RDA

RDB

SG

TX+

TX-

RX+

RX-

SG

120 120

Cable connection when ALR121 is used with RS485 with Multipoint Communication [ 1:N ], 2-wire connection is as follows,

ALR121 Subsystem-1 Subsystem-2 Subsystem-n

SDA

SDB

RDA

RDB

SG

SDA

SDB

RDA

RDB

SG

TX+

TX-

RX+

RX-

SG

120

SDA

SDB

RDA

RDB

SG

120

Different Models of MODBUS PLC require different wiring for cables, the user’s manual for MODBUS PLC must be referred to for individual subsystem connections.

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3.6.1 Cable Specifications for RS-422/RS-485 Communication Links

The standard length for the Communication cable is limited to 100 Meters or less, for the CENTUM systems to allow for the faulty communication caused by noise in the field. However the communicable cable lengths can be extended till 1200 meters, as per the following recommended cable specifications.

Recommended Specifications of Connection Cables:

• Cable type: Shielded twist pair • Number of pairs: 3 • Insulation resistance (at 20°C): 10,000 M ohm·km or greater • Withstanding voltage: 500 V DC for 1 minute • Capacitance (at 1 kHz): 60 pF/m or less • Characteristic impedance (at 1 MHz): 100 ± 10 ohm • Conductor resistance (at 20°C)

Connection of 100 m or less: 54.5 ohm/km or less Connection of 500 m or less: 36 ohm/km or less Connection of 1200 m or less: 17.2 ohm/km or less

3.7 Transmission specifications

Item Description Project Default Settings

Remark

Interface RS-422 / RS485 RS422 or RS485 Transmission method Half Duplex Half Duplex

Synchronization method Asynchronous (Start –Stop Synchronization)

Asynchronous (Start –Stop

Synchronization)

Baud rate 1200, 2400, 4800, 9600, 19200 bps

19200 (*1)

Transmission procedure Modbus protocol (RTU mode)

Modbus Protocol (RTU)

Binary Binary

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Data type

Start bit 1 1

Data bit 8 8

Parity bit None, Even, Odd Even (*1)

Stop bit 1 1

Time monitoring

Transmission enable monitoring time

1000 ms 1000 ms

Reception character interval monitoring time

10 ms 10 ms

Text frame

Start of text None None

End of text None None

XON/XOFF flow control No No

RS control No No (*1)

DR check Yes Yes (*1)

CD check No No (*1)

No response time 0 to 99 seconds 4 (*1)

Number of communication retries upon error

0 to 99 times 4 (*1)

Recovery communication time interval

0 to 999 seconds 30 (*1)

Transmission wait time 1 second 1 second

Note: *1 This can be changed using the ALR121 card -property dialog box from CS3000 System

Builder

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3.8 CS3000: Setting items for ALR121

• Connection Device – Set [MODBUS] as the type of connection device (subsystem).

• Baud Rate – This sets the baud rate between the communication module and MODBUS

PC. The recommended setting for baud rate is [19200 bps].

• Parity – This sets the method for checking the parity of the subsystem data to be transmitted. The recommended setting for the parity is [Even].

• Data Bits – This sets the data bit length of the subsystem data to be transmitted. When using MODBUS PLC, select [8 bits] for the data bit length.

• Stop Bits – This sets the stop bit of the subsystem data to be transmitted. When using the MODBUS PLC, select [1 bit] for the stop bit.

• RS Control – This sets whether or not RS control is performed during subsystem data transmission. When using MODBUS PLC, disable [RS Control] by leaving the [RS Control] check box unchecked.

• DR Check – This sets whether or not DR check is performed during subsystem data transmission. For MODBUS PLC, it is required to enable the DR check by checking [DR check] check box.

• CD Check – This sets whether or not CD check is performed during subsystem data transmission. When using MODBUS PLC, disable [CD Check] by leaving the [CD Check] check box unchecked.

Note: The following figure shows all the above settings as it appears on the ALR121 Module properties.

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3.9 Subsystem Addressing and Function Codes

“Device & Address” and “Data size” are designated on the Communication I/O Builder to access devices. In the case of a Modbus PLC, addresses have the following structure:

<Function code> + <device type> + <address of the device>

For example, when designating input relay 10012 to 10015 on the Communication I/O Builder, A10012 is set as the “Device & Address” and 1 is specified as the “Data size,” Where the “A” of “A10012” corresponds to the function code, “1” to the device type and “0012” to the address of the device.

The range of device address and Modbus protocol function codes for the accessible devices are listed in the following table.

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Meaning of the function code is indicated below:

• A: Read: Read a packet of data designated on the Communication I/O Builder in word units.

Write: Write a packet of data designated on the Communication I/O Builder. With read back.

• B: Read: Read a packet of data designated on the Communication I/O Builder in word units.

Write: Only write the changed single bit device or single word device to the subsystem. With read back.

• X: Write: Write a packet of data designated on the Communication I/O Builder only once when the change occurs. No read back.

• Y: Write: Only write the changed single bit device or single word device once when the change occurs. No read back.

3.10 Time Synchronization With Subsystem

Time Synchronization between CS3000 System and Subsystem shall be achieved as follows.

1. DCS as Master.

At a preconfigured time say at 00:00 Hrs A DO is raised (pulse duration is for minimum 3 second) through SEBOL Program. This DO is hardwired to the DI of the subsystem. 2. Sub-System as Slave.

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When the Sub-System receives the DI (Hardwired pulse of minimum 3 second duration) from the DCS, it resets its time appropriately.

The CS3000 HIS and FCS are connected by Vnet and there is a hardwiring of DO between the subsystem and CS3000 for this purpose.

SEBOL program shall be running always. The program will be checking the time and at specified time, the DO will be set (a 3 second pulse).

V- NET Cable

HIS

FCS Hard Wired DO

Subsystem

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3.11 Setting Items on Communication I/O Builder

Element- With respect to the address of the subsystem data buffer, the element numbers are displayed on Communication I/O Builder. The element number is not for set, only for display.

Buffer- This sets the buffer for the communicated data. This is a required setting item of the Communication I/O Builder.

Program Name- Set the unit number, slot number and MODBUS as program name in the following format:

u-s: Program Name

u: Unit number

s: Slot number

Program Name: MODBUS

Size -This item sets the data size (data length) from the head address set in “Device & Address.”

For MODBUS PLC the setting ranges are limited as follows, the unit is in Word.

For analog input and analog output: 1 to 124 words

For discrete input and discrete output: 1 to 8 words

Station-This sets the station number of the MODBUS PLC. The station numbers that can be set are 1 to 255.

Note: The Subsystem Supplier shall identify the MODBUS Station Numbers.

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Device & Address- Set the head address of MODBUS PLC data.

The addresses can be set using 3 to 7 alphanumeric characters in the formats given below: There is no default setting.

• Coil: A0xxxx, B0xxxx

• Input relay: A1xxxx

• Input register: A3xxxx

• Holding register: A4xxxx, B4xxxx,

“xxxx” is the address within the MODBUS PLC device. The range is 1 to 65535 (1H to FFFFH) and is set as a decimal or hexadecimal number. If it is set with a hexadecimal number, add “H” at the end. Also, with respect to the “xxxx” portion, the 0 prefixed at the head can be omitted. For example, A023, A0023 and A00023 are all the same address for the coil.

Data Type-This sets data type of the subsystem data. The data type can be selected from the following:

• Input (16-Bit Signed)

• Input (32-Bit Signed)

• Input (16-Bit Unsigned)

• Input (32-Bit Unsigned)

• Input (32-Bit Floating)

• Output (16-Bit Signed)

• Output (32-Bit Signed)

• Output (16-Bit Unsigned)

• Output (32-Bit Unsigned)

• Output (32-Bit Floating)

• Input (Discrete)

• Output (Discrete)

Reverse- This sets whether or not to make the bit arrangement in FCS in reverse order of the subsystem data. The following settings can be selected:

• Bits [ Yes/ No]

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Scan- Set whether to read the communication I/O Analog data into the communication I/O data buffer at the beginning of high-speed scan of the FCS.

The default value Scan setting is 1 Second.

Service Comment -A text comment can be set.

Label- The name of the function block I/O terminal can be set as a user-defined label.

3.12 System Alarm Message

This section explains system alarm messages that are specific to the communication module (ALR111, ALR121) as well as those that occur when downloading a sub-system program into the communication module.

3.12.1 System Alarm Messages

System Alarm Messages when the Communication Module is Abnormal:

When the communication module is abnormal, the system alarm message shown below is displayed on the HIS.

FCSxxxx IOM Fail FIOmm NODEnn SLOTyy

FCSxxxx IOM Configuration Error FIOmm NODEnn SLOTyy

• FCSxxxx : FCS name

• mm : FIO number

• nn : Node number

• yy : Slot number

System Alarm Message when the Communication Module Returns to Normal:

When the communication module returns to the normal state, the system alarm message shown below is displayed on the HIS:

FCSxxxx IOM Recover FIOmm NODEnn SLOTyy


• mm : FIO number


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Message when Downloading Starts:

When the subsystem program begins downloading to the communication module, the system alarm message shown below is displayed on the HIS:

FCSxxxx IOM Load Start FIOmm NODEnn SLOTyy


• mm : FIO number



Message when Downloading Ends Normally:

When downloading of the subsystem program to the communication module is completed normally, the system alarm message shown below is displayed on the HIS:

FCSxxxx IOM Load Complete FIOmm NODEnn SLOTyy


• mm : FIO number



Message when Downloading Ends Abnormally:

When downloading of the subsystem program to the communication module is completed abnormally, the system alarm message shown below is sent to HIS:

FCSxxxx IOM Load Error FIOmm NODEnn SLOTyy Error= ####

• FCSxxxx: FCS name

• mm : FIO number



• ####: Error code

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3.12.2 Communication Error Codes

The following are the error code types for the communication error code of Modbus,

Note: *1: ALR121’s definition check error. If this error occurs, no communication can be performed to the Modbus Subsystem.

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Note: *2: This is error when an error message is received from the Modbus PLC. Refer to Third party PLC supplier error message table.

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3.13 Subsystem I/O mapping

3.13.1 I/O Mapping Principle

Exchanging data between the DCS and a subsystem is done in a MASTER/SLAVE relationship, whereby the DCS is always the master.

The number of communication commands messages that can be sent by the DCS is limited to 30, and the total number of words of these messages may not exceed the limit of 1000 words (refer to section 3.3 DCS Communication Capacities).

Each message command transfers a sequential part of memory either from the subsystem to the DCS or the other way around. Please refer the following figure

The total number of words per command message that can be sent depends on the type of message used, as described in section 3.3 DCS Communication Capacities. To optimize for the maximum amount of data to be transferred, it is advisable to use the maximum amount of possible words per command. This approach will limit the amount of command messages and the total overhead time needed for each command message transfer.

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To improve speed it is advisable to keep the data for each call in a contiguous range.

3.13.2 Accessing Subsystem Data from a Function Block

Subsystem data can be acquired from the regulatory control block, sequence control block, SFC block and other function blocks using the subsystem communication package. Also, data can be set into the subsystem from function blocks by using the subsystem communication package.

3.13.3 Overview of Accessing Subsystem Data

Accessing subsystem data varies according to the type of communication module used.

The figure below shows the flow of data between function blocks and subsystem.

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The method for accessing subsystem data from a function block will vary depending on the subsystem data I/O type as follows:

3.13.4 Access in case of Analog input from subsystem

The subsystem data can be treated as analog input signal just like with an analog input module, by specifying the subsystem data address in the format %WWnnnn and assigning it to the input terminal of a regulatory control block. The Input Signal conversion is required to set to “Subsystem Conversion “ in the function block detail definition builder.

TAG_1

PVI

%WW0001

IN

Subsystem[Analog Input]

16 Bit data

The signal conversion follows the equation: PV (fcs) = PV (Subsys.)* GAIN + BIAS PV (fcs): Data after input conversion (PV value of the function block) PV (Subsys.): Raw data from the Subsystem. GAIN: Data conversion gain (7 digits including sign and decimal, 1.000 as the default) BIAS: Data conversion bias (7 digits including sign and decimal, 0.000 as the default) For more illustration on the above, please see the example below,

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Example: The input scale range used for Analog input from a subsystem is as follows: Subsystem Serial Link DCS (100%) SH 4096 4096 SH (100%) (0%) SL 819 819 SL (0%)

• SH/SL: Engineering Scale High/Low Gain/Bias calculation:

For correct indication on the DCS block, the Subsystem inputs have to be corrected as follows:

100 = 4096 * GAIN + BIAS 0 = 819* GAIN + BIAS

Therefore, GAIN = 100 / (4096 - 819) = 0.030516 BIAS = -(0.030516 * 819) = -24.9924

3.13.5 Access in case of Analog output to the subsystem

The subsystem data can be output to the subsystem as a manipulated output vale (MV) of the regulatory block just like with the analog output module by specifying the data in the format %WWnnnn and assigning it to the output terminal of a regulatory block.

TAG_2

MLD

%WW0033

OUT

Subsystem[Analog Output]

16 Bit Data

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In this case, the function block performs the conversion according to the following equation for the communication output data. This is referred to as the communication output conversion:

MV(Subsys.) = (MV(fcs) – BIAS) / GAIN Where, MV(Subsys) = value to be set in the subsystem MV(fcs) = value output from the function block (the MV value of the function block) GAIN = gain for data conversion (7 digits including sign and decimal ,1.000 as the default) BIAS = bias for data conversion (7 digits including sign and decimal , 0.000 as the default)

3.13.6 Access in cases of discrete input and output to and from the subsystem

The subsystem data is specified in the format %WBnnnnbb, as each word of (16 bits) can be assigned to discrete inputs or discrete outputs. I/O number identifies the subsystem data. The DI number is the I/O number for discrete input and DO number is the I/O number for discrete output. In this case, MSB (Most significant bit) corresponds to the smaller DI or DO number and LSB (Least significant bit) corresponds to the larger DI or DO number.

In some cases, depending on the subsystem, this correlation is reversed. Because of this, it is possible to set LSB and MSB reversal via communication IO builder.

If bit reversal is specified in the communication IO builder, when the data obtained via communication is stored in the communication IO data storage area, the order of data reverses in 16-bit units so that at the connection destination, what was the MSB becomes the LSB. The figure below illustrates bit reversal:

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4 Sub-Systems used in the Project. Sub-systems in the “DCS & ESD SYSTEMS FOR PQA PTA PROJECT” are listed below along with their slave addresses.

Baud Rate: 19200 bps.

SUBSYSTEM SLAVE

ADDRESSPackage Package Name TBA TBA 1 TBA TBA 2 TBA TBA 3 TBA TBA 4 TBA TBA 5 TBA TBA 6 TBA TBA 7 TBA TBA 8 TBA TBA 9 TBA TBA 10 TBA TBA 11 TBA TBA 12 TBA TBA 13 TBA TBA 14 TBA TBA 15 TBA TBA 16 TBA TBA 17 TBA TBA 18 TBA TBA 19 TBA TBA 20 TBA TBA 21 TBA TBA 22 TBA TBA 23 TBA TBA 24

Note: The subsystem package list is to be furnished by the client.

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5 Sub-System Mapping Format The Sub-System Vendor has to provide the sub-system tags database as per the following sample format for mapping in DCS:

SL. No.

PLC Tag

Description

Subsystem (PLC) Range

Engg Unit

(PLC)

DCS Tag No.

DCS Range

Engg Unit

(DCS)

Data Type

Subsystem.

station No.

Subsystem

Address

Bit Reversal

LO HI LO HI

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