Content      ..      1       2         ..

HNC-8 Numerical Control System Software. Maual of PLC Programming (V1.24) - page 1

HNC-8-PLC Programming specification

1. PLC Summary

Specifications of PLC

Specificatio

Different PLC types have different program capacities,

function

instruction

ns

counts, and usage range of register.

Specification

HNC8

Programming language

Ladder，STL

Execution cycle of the first level

1ms

program

Program capacity

Ladder program

5000 lines

Statement list

10000 rows

Symbol name

1000

Instruction

Basic instruction,

Function instruction

Internal relay of single byte（R）

400 bytes (R0~~R399)

Internal relay of double-byte（W）

400 bytes (W0~~W199)

Internal relay of four-byte（D）

400 bytes (D0~~D99)

Timer （T）

128 （T0~~T127）

Counter （C）

128

(C0~~C127）

Subprogram （S）

——

Label

（L）

——

User-defined parameter （P）

200 （P0~~P199）

Holding storage area

Timer （T）

128 （T300~~T427）

Counter （C）

128 （C300~~C427）

Four-byte register（B）

200 bytes（B0~~B49）

I/O module（X）

X0~~X512

（Y）

Y0~~Y512

4

HNC-8-PLC Programming specification

1. PLC Summary

Sequential Program

PLC sequential control is achieved by software, and the principle of it is

different from that of common relay circuit. Thus, the principle of sequential

control should be fully understood at the time of designing PLC sequential

program.。

Execution

In general relay control circuit, each relay may operate at the same time. In the

of

figure below, when relay A acts, relay D and E can act at the same time (in the

sequential

event of contact B and C being closed). In PLC sequential control, relays act in

program

sequence. When relay A operates, relay D operates first, and then relay E

operates (see figure 2.1(a)), that is, each relay operates in the order described in

the ladder diagram.

Figure 2.1 (a)

Figure A and B show the movement difference between relay circuit and PLC

program.

Figure2.1（b）

Relay

The actions in figure 2.1b(A) and figure 2.1b(B) are the same. After A (button

circuit

switch) is turned on, B and C are on, with current flowing through coil B and C.

B is cut off after C is switched on.

7

HNC-8-PLC Programming specification

1. PLC Summary

Sequential program consists of three parts: initialization program, the first level program, the

second level program.

The initialization program is performed once when system starts.

The first level program executes every 1ms.

If the first level is longer, the total execution time will be longer. Therefore, you should document

as short program of the first level as possible. The second level program can be automatically

seperated into n parts, and executes every n ms.

Segmentation of the second level program

Segmentation of the second level program is to execute the first level program. When the number

of segmentations is n, the implementation process is as below diagram:

9

HNC-8-PLC Programming specification

1. PLC Summary

When the last part of the second level program has executed, the program starts from the

beginning again. In the event of n segmentations, the time for one loop execution is n ms (1ms X

n). The first level program executes every 1ms, and the second level program executes every n X

1ms. If the steps of the first level program increases, the steps of the second level program will

correspondingly decrease within 1ms, then more segmentations will be gotten, and program

processing time will be longer. For this reason, the first level program should be documented as

briefly as possible.

The first level program only handles short pulse signal, which includes emergency stop, axis

over-travel, and the like.

When subprogram is used, sequential program consists of:

10

HNC-8-PLC Programming specification

1. PLC Summary

Sequential Program Composition

Compositio

For traditional PLC, ladder diagram can be only established sequentially. The

n

ladder diagram language, which allows structured program, has the following

advantages:

‹

The program is easily to be understood and documented.

‹

It is more convenient to find out programming errors.

‹

It is easy to find out reasons of causing errors.

There are three main structured programming means

Subprogra

m

Subprogram regards the ladder diagram block as the processing unit.

Nesting

The combination of documented subprograms forms structured program.

Conditiona

l branch

Main program executes recurrently and detects whether condition is satisfied or

not. If condition is satisfied, corresponding subprogram is executed; if condition

is not satisfied, corresponding subprogram is not executed.

12

HNC-8-PLC Programming specification

1. PLC Summary

13

HNC-8-PLC Programming specification

1. PLC Summary

Address

Address

Address is used to differentiate signals. Various of addresses correspond to input

Definition

and output signals of machine and CNC, internal relay, counter and the like. The

address is composed of address No. and bit No.

Address No.

Address

format

Bit No.

A word must be specified to the left of address No., to express the signal types as

below table:

Register

Signal

Range

X

Input signal from machine

X0~~X512

Y

Signal output from PLC to machine

Y0~~Y512

F

Input signal from NC

F0~~F3119

G

Signal output from PLC to NC

G0~~G3119

R

Internal relay of single byte

R0~~R399

W

Internal relay of double-byte

W0~~W199

D

Internal relay of four-byte

D0~~D99

B

Outage hold relay

B0~~B49

P

User-defined parameter

P0~~P199

Counter（Those after C300 can be held after

C0~~C127

C

usage.）

C300~~C427

Timer

T0~~T127

T

（Those after T300 can be held after usage.）

T300~~T427

L

Label number

——

S

Subprogram number

——

14

HNC-8-PLC Programming specification

2. Basic instruction

Basic Instruction

Sequential program is mainly composed of coil, contact, symbol and function

block. The segments, by which elements of ladder diagram are jointed, form the

logical relationship of sequential program. Sequential program can be described

by ladder diagram language, as well as statement list language which is written

by mnemonics (LD, AND, OR, etc.) and register address. Ladder diagram is

written by coil contact of relay and function block.

As the international standard of IEC61131-3 lays out, ladder diagram language

and statement list language can convert each other logically, and ambiguity

caused by this can be avoided through some programming methods. In

HNC_LADDER_WIN(V1.0) editing software, you can see that the two

languages can mutually transform.

To better understand documenting and inner-making of sequential program, and

to avoid errors in logic or understanding, see the explanation of basic concepts as

following:

Type:

PLC instruction of series

8 is divided into basic instruction and function

instruction.

Basic instruction

Basic instruction is the most basic and most common part of sequential program,

with a total of 19. It executes one-bit manipulation.

Function instruction

Function instruction can perform the functions that is hard to be done by basic

elements, and it can simplify programming.

Storage of logical outcome (ST)

Stack register (to store the intermediate result calculated)

Result being executed

Storage of logical outcome is a stack-like structure. Result of the current

instruction is saved in ST0. When reading instruction such as LD and LDI

appears, result of current instruction is needed to be saved in stack. When ANB

or ORB instruction is encountered, the storage makes ST1 result out stack and

15

Content      ..      1       2         ..

//////////////////////