Selectron LD-007 Manual de Instruções descarregar pdf (Página 103)

The number of times any particular bit can be assigned to conditions is not

limited, so use them as many times as required to simplify your program.

Often, complicated programs are the result of attempts to reduce the number

of times a bit is used.

Except for instructions for which conditions are not allowed (e.g., INTER-

LOCK CLEAR and JUMP END, see below), every instruction line must also

have at least one condition on it to determine the execution condition for the

instruction at the right. Again, diagram A , below, must be drawn as diagram

B. If an instruction must be continuously executed (e.g., if an output must

always be kept ON while the program is being executed), the Always ON

Flag (SR 25313) in the SR area can be used.

Instruction

25313

Instruction

Diagram A: Incorrect

Diagram B

Address Instruction Operands

00000 LD 25313

00001 Instruction

There are a few exceptions to this rule, including the INTERLOCK CLEAR,

JUMP END, and step instructions. Each of these instructions is used as the

second of a pair of instructions and is controlled by the execution condition of

the first of the pair. Conditions should not be placed on the instruction lines

leading to these instructions. Refer to Section 5 Instruction Set for details.

When drawing ladder diagrams, it is important to keep in mind the number of

instructions that will be required to input it. In diagram A, below, an OR LOAD

instruction will be required to combine the top and bottom instruction lines.

This can be avoided by redrawing as shown in diagram B so that no AND

LOAD or OR LOAD instructions are required. Refer to 5-6-2 AND LOAD and

OR LOAD for more details and Section 7 Program Monitoring and Execution

for further examples.

00000

00001 00207

00207

00001

00000

00207

Diagram A

Diagram B

Address Instruction Operands

00000 LD 00000

00001 LD 00001

00002 AND 00207

00003 OR LD ---

00004 OUT 00207

Address Instruction Operands

00000 LD 00001

00001 AND 00207

00002 OR 00000

00003 OUT 002

Programming Precautions Section 4-9

1 2 ... 98 99 100 101 102 103 104 105 106 107 108 ... 367 368

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