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Programmable Controller With Distributed Processing Capabilities Using the SLA Structure

IP.com Disclosure Number: IPCOM000046154D
Original Publication Date: 1983-Jun-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Davis, GT: AUTHOR

Abstract

Programmable controllers have been applied extensively in industrial automation applications. A prime reason for this success is the customer interface. The customer is permitted to generate the application program in a form which is familiar to him, such as Boolean logic expressions or relay ladder diagrams. The SLA (sequential logic array) controller also provides such a user interface, and then provides hardware which is optimized to execute this form of application program. Thus, the SLA structure is adapted for use in a general-purpose programmable controller, and provides a programmable controller architecture which is optimized for distributed processing in large systems.

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Programmable Controller With Distributed Processing Capabilities Using the SLA Structure

Programmable controllers have been applied extensively in industrial automation applications. A prime reason for this success is the customer interface. The customer is permitted to generate the application program in a form which is familiar to him, such as Boolean logic expressions or relay ladder diagrams. The SLA (sequential logic array) controller also provides such a user interface, and then provides hardware which is optimized to execute this form of application program. Thus, the SLA structure is adapted for use in a general- purpose programmable controller, and provides a programmable controller architecture which is optimized for distributed processing in large systems.

The SLA architecture provides several features which allow the system to satisfy many applications that are beyond the range of existing programmable controller performance. For example, the architecture implements a general purpose scanning sequence similar to the scanning sequence of a conventional programmable controller, but with a response time which is ten times faster. If that response time is still not adequate for a particular application, the architecture permits control of the scanning sequence as a function of the results of solving the previous logic expression. Response times as low as one microsecond can be achieved to a specific set of input changes, making the controller competitive with custom hardware interfaces in many applications. Another feature is the capability to partition any or all of the 512 possible logic expressions to generate as many as 2048 smaller expressions, each with only a subset of the inputs and outputs controlled by the card. Features such as these help to provide a powerful solution to many varied applications.

The SLA controller is illustrated in the drawing and is made up of a number of diverse sections. The major functional blocks and how they are interconnected to implement a programmable controller attachment are illustrated in the drawing. These major components include: a. Communications Link Interface 1 b. Local User Interface 2

c. Logic Array Structure 3

d. State Sequencer 4

e. Microcontroller 5

f. Power Supply 6

The communications link interface 1 provides an interface between the programmable controller and the rest of a distributed processing network. A ring- or loop-type communications network provides maximum flexibility for the system. The microcontroller section 5 is the nucleus of the controller, interconnecting the other pieces of the system. The logic array structure 3 solves the basic control equations, while the state sequencer 4 controls the order in which those equations are processed. The local user interface 2 buffers the logic array structure 3 outputs...