LG Electronics 120S user manual Communication Functions Execution of commands

Chapter 8 Communication Functions

8.1.6 Execution of commands

1) Individual reading of device(R(r)SS)

(1) Introduction

This is a function that reads PLC device specified in accord with memory data type. Separate device memory can be read up to 16 at a time.

(2) PC request format

Format name

Header

Station

Command

Command

Number

Device

Device name

......

Tail

Frame

No.

type

of blocks

length

check

Ex. of frame

ENQ

H20

R(r)

SS

H01

H06

%MW100

EOT

BCC

ASCII value

H05

H3230

H52(72)

H5353

H3031

H3036

H254D57313030

H04

1 block(setting can be repeated up to max. 16 blocks)

Item

Explanation

When command is lowercase(r), only one lower byte of the value resulted by adding 1 Byte

each to ASCII values from ENQ to EOT is converted into ASCII and added to BCC. For

BCC

example, the BCC of the above frame is gotten as below:

H05+H32+H30+H72+H53+H53+H30+H31+H30+H36+H25+H4D+H57+H31+H30+H30+H04

=H03A4 Therefore BCC value is A4.

Number of

This specifies how much of the blocks composed of "[device length][device name]" are in this

request format. This can be set up to 16. Therefore, the value of [Number of blocks] must be

Blocks

set between H01(ASCII value:3031)-H10(ASCII value:3030).

Device length

This indicates the number of name's characters that means device, which is allowable up to 16

characters. This value is one of ASCII converted from hex type, and the range is from

(Length of

H01(ASCII value:3031) to H10(ASCII value:3130). For example, if the device name is %MW0,

device name)

it has 4 characters to be H04 as its length. If %MW000 characters to be H06.

Device name

Address to be actually read is entered. This must be ASCII value within 16 characters, and in

this name, digits, upper/lower case, '%' only is allowable to be entered.

Remark

‘H’ of example frame represents hex value, and is unnecessary during preparing real frame.

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