Modbus TCP and RTU on the securityProbe

MODBUS RTU is a non-proprietary serial communications protocol that is widely control industry actuation. The hardware over which MODBUS RTU communications not defined by the protocol.

MODBUS RTU is supported on RS-232, RS-422, RS- other electrical standards. The securityProbe supports RS-232, RS-485 and Ethernet. Modbus/RTU protocol defines how a "master" device polls one or more "slave" devices write data in real time over RS-232, RS-422, or RS-485 serial data communication.

Modbus/TCP, an extension of Modbus/RTU, defines how Modbus/RTU and Modbus/ASCII messages are encoded within and transported over TCP/IP-based networks.

Modbus/TCP is just as simple to implement and flexible to apply as the original Modbus/RTU.

The securityProbe can represent both "master" and "slave" devices and supports both Modbus RTU and Modbus TCP protocols.

Transactions on Modbus Networks

Controllers communicate using a master-slave technique, in which only one device (the master) can initiate transactions (called "queries"). The other devices (the slaves) respond by supplying the requested data to the master, or by taking the action requested in the query. Typical master devices include host processors and programming panels. Typical slaves include programmable controllers.

The master can address individual slaves, or can initiate a broadcast message to all slaves. Slaves return a message (called a "response") to queries that are addressed to them individually. Responses are not returned to broadcast queries from the master.

The Modbus protocol establishes the format for the masters query by placing into it the device (or broadcast) address, a function code defining the requested action, any data to be sent, and an error-checking field. The slaves response message is also constructed using Modbus protocol. It contains fields confirming the action taken, any data to be returned, and an error-checking field. If an error occurred in receipt of the message, or if the slave is unable to perform the requested action, the slave will construct an error message and send it as its response.

Setting up MODBUS on the securityProbe

Settings in the securityProbes web interface

Adjusting the Modbus readings in the securityProbe

Sensor Style - Set the Sensor Style to Analog

Set Time to Polling

Return value from Holding Register

The following is a list of what each of the return values from the Holding Register represent:

  1. No Status (Sensor has not been initialized)
  2. Normal
  3. High Warning
  4. High Critical
  5. Low Warning
  6. Log Critical
  7. Sensor Error
  8. Switch Low (Output)
  9. Switch High (Output)

For the INPUT Register

If the sensor is OFFLINE, the INPUT register will return 32767

If the sensor is No Status or Sensor Error, the INPUT register is -32768

AKCP securityProbe 5ES


Compatible with all of the AKCess Pro range of Intelligent Sensors it provides a complete environmental, access control and security monitoring solution. The AKCP securityProbe 5E Standard has a Linux Operating System running an iMX25 CPU.


from 995,00 Euro*