Configuração modbus yokogawa

1 12.06.2009
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.
Subsystem
Modbus-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 Modbus
PLC
Modbus
PLC
Modbus
PLC
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 Communication
Package
Comm. I/O Data
Storage
Control
Functions
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-BY
SIDE
Data Over
Write
SWITCH INSTRUMENT
SEQUENCE TABLE
CONTINOUS CONTROL INSTRUMENT
Read
REDUNDANT
FUNCTION
SUB-SYSTEM
MASTER I/O
IMAGE AREA
BACKUP I/O
IMAGE 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.
Comm
Card
Comm
Card
ALR121 ALR121
CONTROL
SIDE
STAND-BY
SIDE
Data
Overwrite
SWITCH INSTRUMENT
SEQUENCE TABLE
CONTINOUS CONTROL INSTRUMENT
Write
REDUNDANT
FUNCTION
SUB-SYSTEM
Changing
information
MASTER I/O
IMAGE AREA
BACKUPI/O
IMAGE 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
Descr
iption
Subsyste
m (PLC)
Range
Engg
Unit
(PLC)
DCS
Tag
No.
DCS
Range
Engg
Unit
(DCS)
Data
Type
Subsys
tem.
station
No.
Subsys
tem
Addres
s
Bit
Reversal
LO HI LO HI
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