LS Industrial Systems GLOFA G7M-DR30U - Page 235

Chapter 8. Communication Functions
8-9
8.1.6 Command Execution
1) Individual reading of direct variable (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
Frame ENQ H10 R(r) SS H01 H06 %MW100
...
EOT BCC
ASCII
value
H05 H3130 H52(72) H5353 H3031 H3036
H254D57313030 H04
Item Description
Station No.
HEX value is displayed as ASCII 2 bytes in station.
The example above shows H10 that is the case when the station no. 16 of GM7U is requested
data.
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
This indicates the number of device name's characters, which is allowable up to 16 characters.
This value is one of ASCII converted from HEX type,
- If the device name is %MW0, it has 4 characters to be H04.
- If the device name is %QW0.0.0, it has 8 characters to be H08.
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.
Frame check
(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.
Example) BCC of the above frame is obtained as below:
H05+H32+H30+H72+H53+H53+H30+H31+H30+H36+H25+H4D+H57+H31+H30+H30+H04
=H03A4
Therefore, BCC value A4 becomes H4134 (ASCII).
1) ‘H’ of example frame represents HEX value, and is unnecessary during preparing real frame.
2) The device type for each block should be identical; otherwise an error will be occurred.
1 block (setting can be repeated up to max. 16 blocks)
REMARK