Micro OCS Communications
Micro OCS Communications
Modbus Slave Overview 148
Modbus Master Overview 149
Modbus Addressing Table 150
For complete Modbus instructions, please refer to the Help file in Cscape.
Modbus (serial) is a popular, de-facto standard protocol that allows industrial devices from multiple manufacturers
to easily share data in real-time. For Modbus serial communications, the Micro OCS controller can act as either a
Master or a Slave.
Modbus protocol (serial) allows for one master and multiple slaves. The master always initiates the conversation by
sending a request to a particular slave. Only the addressed slave will send a response when the request is com-
pleted. Should the slave be unable to complete the request, it returns the appropriate error response. Should the
slave be unable to respond, the master’s timeout timer expires to provide an indication of No Response.
Modbus Slave Overview
The Modbus slave function block, when used with the appropriate Modem and/or Open Function Blocks, allows the
primary serial port on the controller to act as a Modbus slave. The Modbus function supports both ASCII and RTU
modes of operation across a range of baud rates and protocol frames. Also supported is port activity status, an
inactivity timer, support for call-on exception, and support for store and forward (repeater) operation for radio
modems.
The Modbus Addressing section describes the supported Modbus Commands as well as the Modbus Map for Micro
OCS controller references (%R, %M, etc.).
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