LG Electronics 120S Chapter 8 Communication Functions , 8.1.6 Execution of commands

Chapter 8 Communication Functions
8-9
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
No. Command Command type
Number
of blocks
Device
length Device name Tail Frame 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
Item Explanation
BCC
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
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
Blocks
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
set between H01(ASCII value:3031)-H10(ASCII value:3030).
Device length
(Length of
device name)
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
H01(ASCII value:3031) to H10(ASCII value:3130). For example, if the device name is %MW0,
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.
1 block(setting can be repeated up to max. 16 blocks)