Ampcontrol VAA, User Manual

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VOICECOM USER MANUAL ISSUE 4
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APPENDIX B – Modbus
The VCA is equipped with an RS-485 communication port that allows point-to-point or multi-drop connection to a
control or SCADA system. The protocol used by the VCA is Modbus RTU. Refer to the Installation and Wiring
chapter of this manual for more information on wiring the VCA’s RS-485 port.
Configuration
The following communication parameters must be set before using the RS-485 port:

Baud rate

Parity

Modbus slave address
Refer to the Configuration section of the VCA Operation chapter of this manual for more information on configuring
the Modbus communication parameters.
VCA Modbus Read and Write Functions
The following functions can be performed via the Modbus connection:

Initiate voice messages

Read VCA I/O status

Read VCA configuration settings

Read VCA fault alarms

Read communication line and pre-start alarm status

Read VAA operational parameter and setting values
Most of these functions are self explanatory from the Modbus table. However, some functions, such as initiating
voice messages and reading VAA parameters require some extra explanation.
NOTE: The VCA Modbus table begins at address 0.
Initiating Voice Messages and Voice Message Control
In order to play voice messages using Modbus, the VCA must be in one of two modes:

DI 1-12 + Mbus 13+
Only messages 13 to 255 can be initiated via Modbus. Messages 1 to 12 are initiated via digital inputs 1 to
12.

Modbus 1 – 255
All messages 1 to 255 can be initiated via Modbus.