CA2013668A1 - Method for input output configuration in a programmable logic controller - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A method is provided for configuring a programmable logic controller (PLC) wherein the PLC
verifies that the actual I/O hardware configuration of the PLC matches an I/O configuration specified by the user prior to running a control program on the PLC.
The I/O configuration supplied by the user is collected in a configuration information file. The match test between the actual I/O hardware configuration and the configuration file is performed both before the control program is run on the PLC and continuously during the execution of the control program. Depending on whether or not the user has set a fatal fault flag, if a mismatch occurs at any time between the actual I/O configuration and the requested I/O configuration in the configuration information file, then the PLC either issues a halt or continues to execute the control program while providing diagnostic/error message information to the user.
Advantageously, any memory space in the PLC memory which is not needed to fill the demands of the I/O
request in the configuration information file remains free for other PLC tasks.

Description

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1 30-CF-l025 METHOD FOR INPUT OUTPUT CONFIGURATION
IN A PROGRAMMABLE LOCIC CONTROLLER

BACKGROUND OF THE INVENTION

This invention relates in general to programmable logic controllers and, more particularly, to a method for confi~uring a pro~rammable loeic controller.
Programmable logic contr~llers (PLC's) are a relatively recent development in process control technology. As a part of process control, a pro~rammable logic controller i5 used to monitor input signals from a variety of input sensors which report events and conditions occurring in a controlled process. For example, a PLC can monitor such input conditions as temperature, pressure, volumetric flow, and the like. A control program is stored in a memory within the PLC to instruct the PLC what actions to take upon encounterin~ parti~ular input si~nals or conditions. In response to tnese input signals, the PLC derives and generates output si~nals which are transmitted to various output de~ices to con~rol the process. For example, the PLC issues output si~nals to open or close a relay, rais~ or lower temperature, adjust pressure, or control the speed of a conveyer, as well as many other control functions.

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The more complex the controlled process, the more input and output devices (I/0 points) there are likely to be. Correspondingly, as the complexity of the controlled process increases, the PLC will likely have to dedicate more I10 points to the controlled process.
PLC system memory is consumed by such dedicated I/0 points because an address in main memory is generally set aside for each I/0 point which is defined. Thus the greater the number of I/0 points associated with a particular process, the greater is the consumption of valuable PLC system memory.
Some conventional PLC systems determine the I/0 requirements of the system with respect to a particular controlled process by examinin~ the control point references in the control program for that particular process. In such systems, the PLC will halt the execution of the control program if it is determined that there are not enough I/0 points available to satisfy the needs of the control program.
Unfortunately, in this approach, the maximum number of available I/0 points is dedicated to a particular control program since, until the control program is executed, it is not known how many I/0 points or addresses will actually be required. In this system, valuable main memory may be dedicated to I/0 points which will actually not be used or needed by the control program. This unfortunately means that it is likely that some valuable system memory, which will not actually be used for IlO points, is nevertheless 3n assigned to and dedicated to such purposes and is thus not available for assignment to other functions.

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S MMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide a method for configuring a programmable logic controller in a manner which conserves valuable system memory.
Another object the present invention is to provide a method of configuring a programmable logic controller in which the user's control over the I10 configuration is enhanced.
In accordance with the present invention, a method is provided for configuring a pro~rammable logic controller which is connectable to a plurality of input devices and output devices. The controller employed in the method includes a memory and is capable of executing a control program to control a process. The method includes the steps of providin~
configuration information with respect to the confi~uration of the input devices and output devices to the controller prior to the controller executing the control program. The method further includes the step of the controller executing the control program sub~equent to the providing configuration information step. In one embodiment, the method includes the step of assigning address space in the memory to the input and output devices specified in the configuration information of the providing step, any memory space not assigned bein~ designated non-assigned memory space. This non-assi~ned memory space i5 advanta~eously released for other controller operations.
In accordance with another embodiment of the method of the invention, a method is provided for configuring a programmable lo~ic controller which is connectable to a plurality of input devices and output ~J ~

devices, the controller including a memory and being capable of executing a control program to control a process. This method includes the steps of providing configuration information with respect to the configuration of the input and output devices to the controller prior to the controller executing the control program. such configuration information being designated provided configuration information. The method further includes the steps of determinin~ the actual configuration of the input and output devices, and comparing the actual configuration to the provided configuration information. The method also includes the steps of the controller performing a first action if the actual configuration matches the provided configuration information, and the controller performing a second action if the actual confi~uration fails to match the provided configuration information.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention believed to be novel are specifically set forth in the appended claims.
However, the method of operation of the present invention may best be understood by referring to the following description and accompanying drawings in which:
FIG. l is a block diagram of a programmable logic controller on which the method of the present invention may be executed; and FIG. 2 is a flowchart detailing the steps employed in the method of the present invention.

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DETAILED DESCRIPT~ON OF THE INVENTION

FIG. Z shows a block diagram representation of a programmable logic controller system lO on which the method of the invention may be practiced. System lO
includes a programmable logic controller (PLC) 15 including a central processin~ unit ~CPU) 20 coupled to a main bus 25. A clock 30 is coupled to CPU 20 to provide a time base thereto. A read only memory (ROM) 35 is coupled to main bus 25 to provide CPU 20 with permanent storage in the conventional fashion. A
random access memory (RAM) 40 is coupled to main bus 25 to provide memory space for CPU 20 to conduct PLC
operations and store user programs.
A handheld pro~rammer 60 such as the Series 90-30 hand-held programmer (HHP) manufactured by CE Fanuc Automation N.A., Inc. is coupled to the PLC by a serial port 45 to enable the user to input information into PLC-15. Programmer 60 includes a keyboard 65 on which the user types input information and further includes a small display 70 to permit the user to view the input information while the input information is bein~ keyed into keyboard 65.
A plurality of input and output ports are coupled to a bus 25A which is connected to main bus 25 of PLC
15 by I/O bus interface 55. One or more input expansion boxes such as input expansion boxes 75 and 80 allow multiple input ports to be coupled to main bus 25 as shown in FIG. l. More specifically, expansion box 75 includes a plurality of input ports in the form of bus connector slots (not shown) for receiving respective input c~rds 75A, 75B and 75C
therein, each card having a port address associated therewith. Although for purooses of illustration.
input expansion box 75 is shown as including three ~ , . :

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~ ' i input cards 75A, 75B and 75C, in actual practice box 75 could accommodate more input cards by employing expansion boxes with more slots (input ports) than shown. In addition, expansion boxes can also hold output modules and output modules can incorporate expansion boxes. I/0 modules 50 may also attach directly to processor I/0 bus 25. Each of input cards 75A, 75B and 75C is coupled to a respective input circuit 77A, 77B and 77C. Input circuits 77A, 77B and 77C sense respective conditions and generate input signals which are reported to the input cards respectively coupled thereto. The actual input points monitored by a control program in PLC 15 are located at these input circuits 77A, 77B and 77C, respectively or are coupled thereto.
In a fashion similar to expansion box 75, expansion box 80 includes a plurality of inputs or slots into which input cards 80A, 808 and 80C are pluggable. A plurality of input circuits 82A, 82B and 82C are coupled to input cards 80A, 80B and 80C, respectively, such that information sensed at the respective input points associated with input circuits 80A, 80B and 80C is provided to input cards 80A, 808 and 80C for transmission to and processing by PLC 15.
A plurality of output ports are coupled to main bus 25 of PLC 15 (through bus 25A and I/0 interface 55) via one or more output expansion boxes such as output expansion boxes 85 and 90 which are coupled to main bus 25. That is, in a manner similar to that of input expansion box 75, output expansion box 85 includes a plurality of output ports in the form of bus connector slots (not shown~ for receivin~
respective output cards 85A, 85B and 85C therein, each output card having a respective port address associated therewith. Although for example purposes.

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2, output expansion box 85 is shown as including three output cards 85A, 85B and 85C, in actual practice output expansion boxes 85 may include a greater number of slots to accommodate a correspondingly greater number of output cards. Each of output cards 85A, 85B
and 85C produces a respective output control signal which is processed by an output circuit and then used to control or drive a particular device. More specifically, each of output cards 85A, 85B and 85C is coupled to a respective output circuit 87A, 87B and 87C. Output circuits 87A, 87B and 87C may be alternatively referred to as amplifiers or device drivers which amplify the level of the output control signals provide thereto up to a level sufficient to drive the particular controlled device (not shown~
coupled to the output circuit. The actual output points controlled by th2 control program in PLC 15 ar~
located at these output circuits 87A, 87B and 87C, respectively, or are coupled thereto.
In a manner similar to output expansion box 85, output expansion box 80 includes a plurality of outputs or slots into which output cards 90A, 90B and 90C are plug~able. A plurality of output circuits 92A, 92B and 92C are coupled to output cards 90h, 90B
and 90C, respectively, such that the control si~nals associated with output circuits 90A, 90B and 30C are provided to output cards 90A, 90B and 90C to facilitate control of the devices coupled to the output points associated with such output circuits~
It will be recalled from the earlier discussion that a control program is provided to PLC 15 to control the operation of the PLC with respect to a particular controlled process. PLC 15 is not limited to executing a particular control program. Rather, different control programs may be loaded at different ;; , , . --, :
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30GF-1025 ~3q~ 3 times into PLC 15 to enable PLC 15 to monitor various input points and to issue output control signals to various output points to permit control of different controlled processes.
In the method of the present invention. a user supplied configuration file is provided to PLC 15 prior to the time at which PLC 15 executes the particular control program provided thereto at RAM 40.
This user supplied configuration file contains information as to how many input points and output points are provided by the cards which are presently mounted in the slots in the input and output expansion boxes coupled to main bus 25 and also provides information that ties references in a control program to physical I/0 points. This configuration file may be supplied by the user in at least two different ways.
In one embodiment of the invention, PLC 15 causes display 55 to present the user with a series of questions prior to running the particular process control program stored ;n RAM 40. The user types in the appropriate configuration information on hand held programmer 60. More specifically, PLC 15 prompts the user to key in the number of I10 points (input points and output points) which are associated with the cards which are plugged into the slots in input expansion boxes 75 and 80 and output expansion boxes 85 and 90.
The user is also prompted to supply information indicating in which expansion box slots the cards are installed. Additionally, the user is prompted to key in information which indicates which I/0 references (input addresses and output addresses) are to be assigned to the particular input points and output points. The above described configuration information ." , , : . . , ,,, .:: , `: ' ,: '': :~: : :
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; ::, , - .:: ' is collected into a configuration file which is stored in RAM 40 for later reference by PLC 15.
After the user supplied confi~uration information is provided to PLC 15, PLC 15 configures I/0 points accordin~ to the requests of the user in the user supplied configuration information. That is, PLC 15 assigns I/0 points and I/0 point addresses according to the number of I10 points, slot locations and I/0 point addresses specified in the user supplied confi~uration information. PLC 15 then performs a test to determine if the user supplied configuration information matches the actual hardware configuration present in programmable logic controller system 10.
For example, a test is made to determine if the actual hardware configuration contains a sufficient number of I/0 points to supply the I/0 points requested by the user in the configuration file. If not, a mismatch condition exists. A test is made to determine if each of the I/0 points requested in the user supplied configuration file is actually present in the physical hardware arrangement of PLC system 10. If not a mismatch condition exists.
When PLC 15 prompts the user for configuration information, it also queries the user to indicate a 2S desired state for a fault flag FF. If fault flag FF
is set to 0, this indicates to PLC 15 that in the event of a mismatch between the user supplied configuration information and the actual hardware configuration wherein a particular I/0 point specified by the user is not available in the actual hardware configuration, then this will be considered a fatal fault by PLC 15. In this event, execution of the particular control pro~ram in PLC 15 will halt.
However, if fault fla~ FF is set to l, then this indicates to PLC 15 that this mismatch is not a fatal ", ,",., ":... .

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fault and that execution of the control program should continue except that PLC 15 should provide dia~nostic information. That is. PLC 15 store an error message in RAM 40 to indicate that a mismatch occurred between the user supplied configuration file and the actual hardware configuration of PLC system 10. The user program can take a user defined action on this error condition.
In the present invention, any I/0 points which are not assigned by the user in the configuration file may be used for other purposes. For example, any unassigned output points may be used as internal coils or storage elements. Advanta~eously, assuming that not all of the available I/0 points in a partioular PLC hardware confi~uration are assigned in a confi~uration file, then a portion of RAM 40 need not be assign~d to such non-assigned I/0 points. Valuable system RAM is thus conserved in this manner.
A summary of configuration information which is provided in the confi~uration file is listed below in Table 1. The followin~ types of configuration information are provided for examples purposes. It should be understood that other configuration information which describes tha hardware configuration of PLC 15 could be included as well in the user supplied configuration information.

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TABLE l CONFICURATION FILE CONTENTS

PARAMETER I DESCRIPTION

I NI I number of requested input 1 I points ¦ :
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NO I number of requested output points AI(i) I address of each input point I I requested (i is an index3 1 AO(j~ I address of each output point requested lj i 5 an index) ¦ PSN I physical slot number of which each I and O point is I I associated Alternatively, rather than havin~ the user input the confi~uration file from hand held programmer 60, the configuration file may be stored in a memory included in the particular module or card to be plugged into a slot in HHP 60. Each I/O module contains confi~uration information as well. The configuration information contained in the module in at least one embodiment includes the above described configuration information and also configuration information such as module type, module identification . - ~ , ~ , . ......... . .

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-~ 30GF-1025 2 F~ 3 - l2 -number and the number amount of input points and output points which the particular module provides.
In another embodiment. only the number of IlO points the I/0 mudule provides is stored in the module. This alternative memory storage approach is discussed in more detail in the copending U.S. patent application entitled IlO Verification Method, U.S. Serial No. (30-GF-1025) filed concurrently herewith and assigned to the instant assignee.
From the above description it will be appreciated that the user determines the IJ0 requirements separately from cre tin~ the PLC control program.
These I/0 requirements are provided as configuration information to the PLC separately from the control lS program. In this manner, the user is free to use any unassigned inputs and outputs for other purposes. For ~xample, any ~nas~ign~d outputs m~y b~ usod a~
internal coils or storage elements.
FIG. 2 is a flowchart which depicts the steps in the method of the present invention. First, programmable logic controller system lO is powered on and initialized as in block lO0. Then, a control program is provided to PLC 15 via hand held programmer 60. A configuration file is provided to PLC 15 at block llO. The fault flag FF is set to 0 for fatal fault or l for continueldiagnostics as discussed earlier as per block l15. The PLC then assigns input points and output points as indicated by the input points and output points in the configuration file as per block 120. Any non-assigned I/0 points are then released for other uses at decision block 122 and any non-assigned PLC system memory is released for other uses in block 124. A test is made at decision block 125 to determine if the actual hardware configuration of PLC system lO matches the confi~uration requested , . .
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.,. .-. .. ,. , , in the configuration file. If the requested configuration indicated by the configuration file matches the actual configuration, then the control program is run as per block 130. During the execution of the control program, PLC 15 continually tests to see if the above described match exists as indicated by the return of flow to the decision block 125 from run block 130. If it is at any time determined that the configuration requested in the configuration file does not match the actual hardware configuration, then a decision is made to determine if a fatal fault has occurred as per block 135. If a fatal fault has occurred, namely if fault flag FF = 0, then execution of the process control program halts as indicated at block 140. However, if a fatal fault has not occurred, namely if fault flag FF = 1, then execution of the control program continues and dia~nostics information is provided at block 145 as di~cussed earlier. By setting fault flag FF to 1, a control pro~ram can be run for diagnostics and testing purposes even if no input or output devices are coupled to PLC 15. Appropriate error messages will be issued by PLC 15, but the control program will run~
The fore~oing has described a method for confi~uring a programmable lo~ic controller. In summary, the PLC employed in this method verifies that the actual IlO hardware configuration of the PLC
matches an I/0 configuration specified by the user prior to running a control program on the PLC. This match determination is performed before executing a PLC control program and is performed continuously during the execution of the control program.
Depending on whether or not the user has set a fatal fault flag FF, if a mismatch occurs at any time between the actual I/0 configuration and the requested 30GF-1025 ~ '3 I/0 configuration, then the PLC either issues a halt or continues to execute while providing diagnostic/error messa~e information to the user, In the disclosed invention, any memory space in the PLC
memory whish is not needed to fill the demands of the IlO request in the user provided configuration information remains free for other PLC tasks and control program tasks. In this manner, the disclosed method advanta~eously conserves valuable system memory when a PLC is configured. Moreover, the user's control over the I/0 confi~uration of the PLC is substantially enhanced.
While only certain preferred features of the invention have been shown by way of illustration, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the present claims are intended to cover all such modificatiors and changes which fall within the true spirit of the invention.

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Claims (8)

1. A method for configuring a programmable logic controller which is connectable to a plurality of input devices and output devices, said controller including a memory and being capable of executing a control program to control a process, said method comprising the steps of:
providing configuration information with respect to the configuration of said input devices and said output devices to said controller prior to said controller executing said control program:
assigning address space in said memory to input and output devices specified in the configuration information of said providing step, any memory space not assigned being designated non-assigned memory space;
releasing any non-assigned memory space for controller operations or operations by the user control program; and executing by said controller said control program subsequent to said providing configuration information step.

2. A method for configuring a programmable logic controller which is connectable to a plurality of input devices and output devices, said controller including a memory and being capable of executing a control program to control a process, said method comprising the steps of:
providing configuration information with respect to the configuration of said input and output devices to said controller prior to said controller executing said control program. such configuration information being designated provided configuration information;
determining the actual configuration of said input and output devices:
comparing said actual configuration to said provided configuration information;
said controller performing a first action if said actual configuration matches said provided configuration information: and said controller performing a second action if said actual configuration fails to match said provided configuration information.

3. The method of claim 2 wherein said first action comprises initiating processing of said control program subsequent to said providing, determining and comparing steps.

4. The method of claim 2 wherein said second action comprises halting program operation subsequent to said providing. determining and comparing steps.

5. The method of claim 2 wherein said second action comprises processing said control program and providing diagnostic information subsequent to said providing, determining and comparing steps.

6. The method of claim 2 including the step of assigning address space in said memory to input and output devices specified in the configuration information of said providing step, any memory space not assigned being designated non-assigned memory space.

7. The method of claim 6 including the step of releasing any non-assigned memory space for controller operations or user control program operation.

8. The invention as defined in any of the preceding claims including any further features of novelty disclosed.