ProSoft Technology ProLinx S3964R User Manual download pdf (Page 50)

50 Publication LOGIX-AP010B-EN-P - May 2010

Chapter 2 Software Conversions - Program Structure

Conversion of STEP 5 Code

to RSLogix 5000 Software

For most applications the easiest conversion is to convert the Step 5 program

to RSLogix 5000 software with the same programming language. So a Step 5

program written in ladder logic should be converted to an RSLogix 5000 ladder

program. Similarly, a Step 5 Control System Flowchart should be converted to

an RSLogix 5000 Function Block Diagram program, and a Step 5 Structured

Text program should be converted to an RSLogix 5000 Statement List

program. However, sometimes it is better to consider another language. In Step

5, PLC code was often programmed in STL for execution speed (no internal

translation to native STL language needed) and because it offered more

flexibility and more powerful programming compared to the other languages.

For example, consider RSLogix 5000 SFC programming language if the Step 5

application is mainly a series of discrete steps that must be executed in an easily

defined sequence. Also, the one-shot instruction that did not exist in Step 5

and must be programmed in a STL can easily be done in an RSLogix 5000

Ladder diagram. Another consideration would be the PIDE block that only

exists in FBD language in RSLogix 5000.

RSLogix 5000 programming languages are more flexible and contain a wider

variety of functions than the older Step 5 package. You may reduce converted

code complexity with RS Logix 5000 functions unavailable in Step 5.

For example, Step 5 does not allow mathematical calculations such as addition

and subtraction to be performed on some data types. You cannot add a

floating point number and an integer without first converting them to the

same format. RSLogix 5000 software, however, can perform these

mathematical calculations on other data types.

RSLogix 5000 software also lets the programmer perform multiple

mathematical calculations in one instruction with the Compute (CPT) function

to reduce code size and complexity when converting from Step 5.

Calculation in RSLogix5000 Ladder Diagram

To perform a mathematical operation on two operands in Step 5 Statement

List, load these operands into Accumulator Registers, perform the required

mathematical operation on the Accumulator Registers, and transfer the result

from the Accumulator Register to the desired location. RSLogix 5000

Structured Text performs operations directly on the required tags and

transfers the result directly to the required destination without using

Accumulator Registers as in Step 5.

Calculation in RSLogix5000 Structured Text

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ProSoft Technology ProLinx S3964R User Manual Page 50