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I find myself in trouble for a moment with modbus addressing and in particular reading or writing words on the PLC slimline with a series i operator panel, connected on a serial port.
As for the single bits I have succeeded but I can not write words on the plc or even read them. Obviously I did not understand how it works although with the bit level command it works even if I believe that we can do better. For now I would need the mapping of a dozen words, then I will go into more detail later.
The modbus protocol both TCP on serial and OverIP on ethernet network allows access to all the variables relating to the user memory (MX100), as shown in the manual Programmazione IEC su sistema SLine of which I enclose excerpt.
Warning! Since the allocation of the variables in the PLC memory is performed in byte, while the reading of the registers from modbus is performed in word, to address the PLC variables in the terminal it is necessary to divide the allocation address by 2. For simplification, let's see a variable definition table on the PLC and the relative address in the terminal:
Variables on PLC HMI address
Name Type Address
Var0 UINT% MW100.0 3x 40000
Var1 UINT% MW100.10 3x 40005
Var2 UINT% MW100.100 3x 40050
Var3 UINT% MW100.2048 3x 41024
Var4 UINT% MW100.4094 3x 42047Remember that the memory from% MW100.2048 to% MW100.4095 is retentive memory, therefore the values present in the variables allocated in this range of addresses are maintained when the system is turned off.
I have a system consisting of cpu Slimline MPS054 and a Wintek cMT terminal. To perform a read / write of a bit variable I use an address of the type 0x.
Is it possible to point directly to an output of the plc? For example, the output% QX255.0.
The Modbus protocol on systems SlimLine it only accesses the DB100, so to manage I / O you have to forcibly create a small program that supports its status on BOOL variables allocated in DB100. You will find more information in this topic.
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