A-B 1785-LT3

Classic 1785 PLC5ProgrammableControllers(1785LT, LT2, LT3, LT4)

The program-development portion of your functional specification can be in any form: written statement; flowchart; or rough-draft MCPs,SFCs, and subroutines.  Use the form that is most familiar to you.We recommend, however, that you generate rough-draft SFCs and subroutines so that you have a better correspondence between your beginning diagrams and your finished program.
Detailed Analysis
In this phase, you identify the logic needed to plan your programs.This includes inputs, outputs, specific actions, and transitions between actions (i.e., the bit-level details needed to write your program).
Program Development
You enter the programs either offline into your computer or online into a processor. In the next phase, you test the programs that you have entered. Once testing is complete, your resulting programs should match your functional specification.
Checking for Completeness
When you complete the functional specification and the detailed analysis, review them and check for missing or incomplete information such as:
 ● input conditions
 ● safety conditions
 ● startup or emergency shutdown routines
 ● alarms and alarm handling
 ● fault detection and fault handling
 ● message display of fault conditions
 ●  abnormal operating conditions

Introducing Classic PLC-5 Processor Modules

The following is a list of the PLC-5 processors and their catalog numbers.

For information on other PLC-5 processors (Enhanced, Ethernet, or ControlNet), see your Allen-Bradley representative.

Classic PLC-5 Family Processor Features
From the family ofPLC-5 processors, you can choose the processor(s) that you need for your application.Features common to all Classic PLC-5 processors are:
 ●  same physical dimensions
 ●   use of the left-most slot in the 1771 I/O chassis
 ●   can use any 1771 I/O module in the processor-resident local I/O chassis with up to 32 points per module
 ●   same programming software and programming terminals
 ●  same base set of instructions
 ●  ladder programs and SFCs can be used by any of the PLC-5 processors
Check with your Allen-Bradley sales office or distributor if you have questions regarding any of the features of your PLC-5 processor.
Subprogram Calls
Use a subroutine to store recurring sections of program logic that can be accessed from multiple program files.A subroutine saves memory because you program repetitive logic only once.The JSR instruction directs the processor to go to a separate subroutine file within the logic processor, scan that subroutine file once, and return to the point of departure.
For detailed information about how you generate and use subroutines, see your programming software documentation set.
Sequential Function Charts
Use SFCs as a sequence-control language to control and display the state of a control process. Instead of one long ladder program for your application, divide the logic into steps and transitions.A step corresponds to a control task; a transition corresponds to a condition that must occur before the programmable controller can perform the next control task.The display of these steps and transitions lets you see what state the machine process is in at a given time.

Installation and removal of processor

1：Before you dissassemble the processor, check to ensure that you have a backup copy of the customer program on hard disk or tape.
2：Being careful not to lose the washers, remove the four screws from the plastic cover and note the orientation of the stand-offs and sleeves.

3 : Remove the screw from under the plastic cover.

4 : Being careful not to damage the interboard connector pins, separate the two printed circuit boards.

5 : Replace the firmware PROMs in locations U32, U33, and U38. Observe thepin 1 locater and make certain that no pins are bent under.

6 : If your processor has a protopack device in location U41, replace it withthe masked ROM device included with this update kit. If U41 is already amasked ROM, and the date code on that part is 9242 or earlier, replace it. IfU41 is a maked ROM with a date code of 9243 or later, skip this step.

7 : Reassemble the processor observing the cautions described on the front pageof these instructions.

8 : Reload the customer program and make sure that it runs properly.

Other models：1771-NT2 ，1771-OA ，1771-OAD ，1771-OB ，1771-OBN ，1771-OD ，1771-OD16 ，1771-ODD ，1771-OFE1 ，1771-OFE