Chapter 8. Communication Functions
8-12
2) Continuous reading (R(r)SB) of device
(1) Introduction
This is a function that reads the PLC device memory directly specified in accord with memory data type. With this, data is
read from specified address as much as specified continuously.
(2) PC request format
Format
name
Header
Station
No.
Command
Command
type
Device
length
Device
Number of data
(Max. 128 bytes)
Tail
Frame
check
Frame ENQ H10 R(r)
SB
H06 %MW100 H05 EOT BCC
ASCII
value
H05 H3130 H52(72)
H5342
H3036
H254D57313030
H3035 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.
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.
No. of data
Specifies the no. of data to read continuously from the specified address. The example above
reads 5 words serially from %MW100. Up to 120 data is available for continuous reading.
Frame check
(BCC)
When the command is lowercase(r), only one lower byte of the value resulted by adding 1 Byte
each to the ASCII values from ENQ to EOT is converted into ASCII and added to BCC, and then
sent.
(3) GM7U main unit response format (ACK response)
Format name Header
Station
No.
Command
Command
type
Number
of blocks
Number
of data
Data Tail
Frame
check
Frame (Ex.) ACK H10 R(r) SB H01 H02 H1122 EOT BCC
ASCII value H06 H3130
H52(72)
H5342
H3031
H3134
H31313232 H03
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