51
2017/06
Data model
The data model distinguishes four basic data types:
For each of these basic data types, the protocol allows individual selection of 65536 data items, and
the operations of read or write of those items are designed to span multiple consecutive data items
up to a data size limit which is dependent on the transaction function code.
It’s obvious that all the data handled via Modbus (bits, registers) must be located in device applica-
tion memory.
Access to these data is done via defined access-addresses (see „Modbus Registers“, page 54).
Data type Object type Access Comment
Discrete Inputs Bit Read This type of data can be provided by an I/O system.
Coils Bit read/write This type of data can be alterable by an application pro-
gram.
Input
registers
16-bit
(Word)
Read This type of data can be provided by an I/O system.
Holding regis-
ters
16-bit
(Word)
read/write This type of data can be alterable by an application pro-
gram.
To Next Page
Loading...
Need help?
General
