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Software Interface Description
Protocol Overview
All communications with the Vilter Reciprocating Compressor Controller is on a request-response basis. The main
computer is the “master” and the Viltech controller is the “slave”. All messages will originate on the master with the
slave responding as required.
Status Only or Status and Control Options
The reciprocating compressor microprocessor communications supports two options. When configured for the
Status Only option, the Viltech will only respond to the status message but will not respond to any control or
setpoint messages. When configured for the Status and Control option, the Viltech will respond to all message
types. The Status and Control option is selected by enabling Modbus communications on the Communications
Setup screen. To allow setpoints to be changed, select Yes for the “Allow Network Control” selection. If network
control is not allowed, Status Only is selected and an error response will be returned whenever a control message is
attempted. When network control is allowed, Status and Control is selected and control messages may be used to
control the compressor. The Remote mode is the primary means of control when the Network Control Option is
enabled. Remote mode is enabled on the Control Configuration screen.
Message Categories
Several message categories are supported and described below:
• Status Message
• Compressor Control Message
• Suction Pressure Setpoint Message
• Process Temperature Setpoint Message (Optional)
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