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Commands
If you hold a type IPC03 tag in front of the read/write head, you can read the data by executing
the command
read holding registers
again.
Command: read/write multiple registers (17h)
This MODBUS command combines the functions of the commands
write multiple registers
and
read holding registers
. You should use this command if you wish to systematically
exchange data via the PLC.
If you use this command to execute an identification command (e.g. a read command), you will
not receive the answer in the response associated with this request. The command requires a
certain amount of time to finish processing, after which the data will be available.
You must know the following parameters to make the request:
Writing:
Reading:
The IDENTControl Compact sends a response. If the IDENTControl Compact is scheduled to
execute the command a number of times in succession, change the first four bytes of the
telegram. Remember to set the toggle bit.
7.7.4
Notes for creating the control program
TCP connection:
Many MODBUS masters enable the use of transactions accompanied by a TCP link
connection and disconnection. As outlined in the MODBUS specification, we recommend
maintaining as opposed to terminating the connection following a transaction.
2003d
High byte
Byte 4
Status
05h 05h = identification
read error (meaning of
the identification
statuses see chapter
Low byte
Byte 5
Reply counter
02h Increases by 1 after
each additional
response.
2004d -
2011d
High byte
Data
00h No data read because
no tag in front of the
read head.
Low byte
Data
00h No data read because
no tag in front of the
read head.
Start address (depending on channel)
Channel 0
0d
Channel 1
1000d
Channel 2
2000d
Number of registers to be written:
Maximum 121d
Start address
Start address
Number of registers to be read:
Maximum 125d
Address
(0-based)
Register division
Byte number of the
identification
telegram
Use
Type Meaning
