Editing Modbus (section)

=== Modbus data model ===
Modbus defines its data model based on a series of tables of four primary types:{{Sfn|MODBUS Application Protocol|2012|p=6|ps=, "4.3 MODBUS Data model"}}
{| class="wikitable"
! Primary tables
! Access
! Size
!Features
|-
| Discrete input
| R
|1 bit (0–1)
|Read on/off value
|-
| Coil (discrete output)<ref>{{Cite web |title=Modpoll Modbus Master Simulator |url=https://www.modbusdriver.com/modpoll.html |access-date=2023-10-13 |website=modbusdriver.com |postscript="-t 0" is for "Discrete output (coil) data type"}}</ref>
| R/W
| 1 bit (0–1)
|Read/Write on/off value
|-
|Input register
|R
|16 bit words (0–65,535)
|Read measurements and statuses
|-
|Holding register
|R/W
|16 bit words (0–65,535)
|Read/Write configuration values
|}
For each of the primary tables, 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.{{Sfn|MODBUS Application Protocol|2012|p=6|ps=, "4.3 MODBUS Data model"}}