C ONTROL P ROGRAM P RINTOUT

C ONTROL P ROGRAM P RINTOUT

The control program printout is a hard copy of the control logic program stored in the controller’s memory. Whether stored in ladder form or some other language, the hard copy should be an exact replica of the controller’s memory. Figure 12-6 shows a typical ladder printout in its basic format.

A basic hard copy printout shows each programmed instruction with the associated address of each input and output. This printout, however, does not readily provide information about each instruction’s function or which field device is being evaluated or controlled. For this reason, the program coding alone, without the previously mentioned documentation, is not ad- equate for interpretation of the control system. Most manufacturers provide

a documentation package that allows the programming device, generally a PC (personal computer), to enter labels or mnemonic nomenclature for the control program elements.

The extent of the control program printout and documentation varies from one PLC manufacturer to another. This documentation may or may not include information pertaining to the input/output connection diagram.

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S ECTION PLC PLC System C HAPTER 3 Programming

E>=P ( )

PRESET: 2001 VALUE:

+) DOWN

E<=P ( ) .01

ELAPSED: 2500 VALUE:

E>=P ( )

PRESET: 2002 VALUE:

+) DOWN

E<=P ( ) .03

ELAPSED: 2501 VALUE:

40 RESET .02

Figure 12-6. Ladder diagram printout.

Figure 12-7 illustrates a ladder control program with generic documented elements in the ladder rung. Sometimes, only the I/O address number represents these ladder diagram elements. Most PLC manufacturers’ docu- mentation allows the user to set global or generic mnemonic comments and then cross-reference the mnemonics with the inputs and outputs (real and internal) used in the system.

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S ECTION PLC PLC System C HAPTER 3 Programming

Documentation 12

02 I

I E-STOP

ENGAGE

EVIS OFF

II 04 I

I E-STOP

ENGAGE

EVIS ON

II 06 I

I EVIS OFF PROX SW AIR PRESS SPD FAIL

ENGAGE ON

( ) I SAFETY INTERLOCK FOR ENGAGING

I OF REHANGER 08 I

I EVIS ON 09 II 10

I ON DELAY TIMER I EVIS ON ENGAGE ON 11 ACTIVE TON I 1

I 1 SECOND

I DELAY POT

R 600 13 PRESET ELAPSE

Time Delay Is Taken From Pot 2 14 On The Merge Module. Operator

Can Select From 0-10 Seconds

I 15 II 16 I

Figure 12-7. Ladder control program printout with manufacturer’s documentation.

Most IEC 1131 software systems include a documentation package that uses the defined variables as the labels for the programmed control elements. These systems also provide a summary of the variable declaration and the types of variables declared. Figure 12-8 shows a typical IEC 1131 level 1 chart printout.

The controller’s memory always holds the latest software revision of the program; therefore, the user should have the most recent hard copy when examining the system. Changes are frequently made to the program during start-up, so these changes should be immediately documented, even though this is time consuming. Another good practice is to obtain the latest hard copy of the program after any field changes have taken place.

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S ECTION PLC PLC System C HAPTER 3 Programming

Documentation 12

1 Initialize

Run & Not (Error)

Error

20 Start Motor M1

30 Alarm

M1 Started

Acknowledge

21 Start Tempo

Tempo > 3s

22 Stop Motor M1

M1 Stopped

Figure 12-8. IEC 1131 level 1 chart printout.