The type of register read. This type results in the function codes that will be
used to read and write the data.
The authorised values are:
• 1: “coil . The modbus read function code will be 0x01. The write
function code will be0x05
• 2: “discrete inputs“. The modbus read function code will be 0x03.
This type is for input reading. Writing is therefore not possible.
• 3: “holding register”. The modbus read function code will be 0x03.
The write function code will be 0x10
• 4: “input”. The modbus read function code will be 0x04. As this type
is for input reading, there is no associated write function.
Address and size of the register or input to read.
The possible forms are the following:
• Register address. This is the most common case. Here, we find the
register address in its classic format. Example: “40000” causes the
register to be read at address 40000.
• Register address and size. This format is used to indicate the size of
the data to be read, expressed in bytes. This format is used to read
character strings for example.
The format is the following: Register address_Size.
Thus, for example, the value “40000 10” configures a variable of
which the data is at register 40000 and is 10 bytes long.
• Register address, 1
st
bit and number of bits. This format is used to
indicate the register at which a bit field starts and the bit field size.
Note that if the number of bits is 1, there is no need to indicate the
number of bits.
The format is the following: Register address_1
st
bit_Number of
bits.
Thus, for example, the value “40005_4_8” configures a variable of
which the data is at register 40005 at its 4
th
bit and is 8 bits long.
Similarly, the value “40008_1” configures a variable of which the
data is at register 40008 at its 1
st
bit and of which the value is only 1
bit long considering that the number of bits is not indicated.
Variable type.
The authorised types are the following:
• U8: unsigned integer on 8 bits (1 byte)
• U16: unsigned integer on 16 bits (2 bytes, or 1 register)
• U32: unsigned integer on 32 bits (4 bytes, or 2 registers)
• U64: unsigned integer on 64 bits (8 bytes, or 4 registers)
• I8: signed integer on 8 bits (1 byte)
• I16: signed integer on 16 bits (2 bytes, or 1 register)
• I32: signed integer on 32 bits (4 bytes, or 2 registers)
• I64: signed integer on 64 bits (8 bytes, or 4 registers)
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