ModbusAsyncDevice

This component represents a Modbus serial (async) device under a ModbusAsyncNetwork, and provides client access by the station (acting as Modbus master). In addition to the typical device components, it contains properties to specify the device’s Modbus address, data mode (RTU or ASCII), and other properties, including slots to specify the base address for Modbus data items (holding registers, input registers, inputs, coils), plus a DevicePollConfigTable for device polling.

Figure 9. ModbusAsyncDevice properties

You access these properties by expanding Drivers > ModbusAsyncNetwork and double-clicking the ModbusAsyncDevice in the Nav tree.

In addition to the standard properties (Status, Enabled, Fault Cause, Health and Alarm Source Info), these properties support the Modbus async device:

Property	Value	Description
Device Address	number from 1 to 247	Defines the unique number that identifies the current device object on the network.
Modbus Config	additional properties	Refer to Modbus Config.
Ping Address, Address Format	Hex (default), Decimal, or Modbus	Selects the format of an address used to automatically configure unique register addresses for the device’s points. The driver merges this address with the point address. For an example, refer to Base addresses.
Ping Address, Address	number	Defines the base address to use.
Ping Address Data Type	drop-down list	Defines the type of numeric data.
Ping Address Reg Type	drop-down list	Defines the type of register.
Poll Frequency	drop-down list	Configures how frequently the system polls proxy points.
Input Register Base Address, Address Format	Hex (default), Decimal, or Modbus	Selects the format of an address used to automatically configure unique register addresses for the device’s points. The driver merges this address with the point address. For an example, refer to Base addresses.
Input Register Base Address, Address	number	Defines the base address to use.
Holding Register Base Address, Address Format	Hex (default), Decimal, or Modbus	Selects the format of an address used to automatically configure unique register addresses for the device’s points. The driver merges this address with the point address. For an example, refer to Base addresses.
Holding Register Base Address, Address	number	Defines the base address to use.
Coil Status Base Address, Address Format	Hex (default), Decimal, or Modbus	Selects the format of an address used to automatically configure unique register addresses for the device’s points. The driver merges this address with the point address. For an example, refer to Base addresses.
Coil Status Base Address, Address	text	Defines the base address to use.
Input Status Base Address Format	Hex (default), Decimal, or Modbus	Selects the format of an address used to automatically configure unique register addresses for the device’s points. The driver merges this address with the point address. For an example, refer to Base addresses.
Input Status Base Address	number	Defines the base address to use.
Device Poll Config	additional properties	Device Poll Config
Points	additional properties	Points (client device)

Base addresses

Defining a base address provides a quick way to configure unique point addresses. For example, assume you have 10 of the same devices each with 20 points. Configuring a unique address for 200 points could take a substantial amount of time. To speed configuration, you could configure a single device with all its point addresses set to 01–20, duplicate that device 10 times, then change the base address(es) for each device. The result: all points have unique addresses.

Unique point address example

Device	Base Address	Resulting point addresses
1	100	101, 102, 103, ... 120
2	200	201, 202, 203, ... 220
3	300	302, 302, 303, ... 320
4	400	401, 402, 493, ... 420
etc.	etc.	etc.

This works the same for all the base address properties: Input Register, Holding Register, Coil Status, and Input Status.

Modbus Config

Each client Modbus device object (ModbusAsyncDevice, ModbusTCPDevice, and ModbusTCPGatewayDevice) has an associated Modbus Config container slot to override these network-wide defaults. These properties adjust the settings for message transactions to (and from) only that device.

Property	Value	Description
Override Network	`true` or `false` (default)	Determines which values to use for these properties: `Float Byte Order`, `Long Byte Order` and `Use Force Multiple Coil`. `false` selects the network-level values as configured by the ModbusAsyncNetwork component. `true` selects the values defined by the Modbus Config container slot.
Float Byte Order	drop-down list	Specifies the byte-order used to assemble or receive floating-point (32-bit) values in messages. Choices reflect two alternate methods, where numerals 0, 1, 2, and 3 represent the least significant byte to most significant byte: Order3210 – Most significant byte first, or big-endian, it is the default. Order1032 – Bytes transmitted in a 1,0,3,2 order, or little–endian.
Long Byte Order	drop-down list	Specifies the byte-order used to assemble or receive long integer (32-bit) values in messages. Choices reflect two alternate methods, where numerals 0, 1, 2, and 3 represent the least significant byte to most significant byte: Order3210 - Most significant byte first, or big-endian, it is the default. Order1032 - Bytes transmitted in a 1,0,3,2 order, or little-endian. NOTE: Float or long values received in incorrect byte order may appear abnormally big, or not at all.
Use Force Multiple Coil	`true` or `false` (default)	Specifies whether to use function code 15 (Force Multiple Coils) instead of function code 05 (Force Single Coil) when writing to coils. The default is `false`, where function code 05 (Force Single Coil) is used. This property depends on the Modbus function codes supported by child devices, which (if available) provide alternative options in Modbus messaging. Function code 15 support (Preset Multiple Coils) is available in devices (true or false). The default is `false`, where function code `Preset Single Coil` is in place.