Registers
Modbus bases its data model on a series of tables that have distinguishing characteristics. The following are the four primary tables:
| Table | Description |
|---|---|
| Discrete Inputs | Single bit; Read-Only. This type of data can be provided by an I/O system. |
| Coils | Single bit; Read/Write. This type of data can be alterable by an application program. |
| Input Registers | 16-bit word; Read-Only. This type of data can be provided by an I/O system. |
| Holding Registers | 16-bit word; Read/Write. This type of data can be alterable by an application program. |
The protocol allows for the individual selection of 65,536 data items for each primary table.
In Vision Builder AI, all four register tables are distinct in memory, do not overlap, and start at address 0x00000.