User Tools

Site Tools



Set Modbus

Set Modbus mode, slaveAddress, returnInterval

mode 0=ASCII, 1=RTU
slaveAddress Slave address (1 to 254)
returnInterval Return interval (1 to 255)

Cubloc supports the Modbus protocol in combination with Ladder Logic functions. Modbus can be used on RS-232 channel 1 only.

To enable Modbus slave mode, use the Set Modbus command. This command will enable the Modbus slave. It must come after an OpenCom command to set up RS-232 communication on serial channel 1. The baud rate, stop bit, and parity settings can be set with OpenCom.

The Modbus slave uses the Ladder Logic registers (P, D, M, etc…) as its data source, so even if only BASIC is used, the Ladder Logic scanner must be turned on to copy data to and from the physical hardware and the Ladder Logic registers.

OpenCom 1,115200,3,80,80     ' Please set receive buffer to at least 50.
Set Modbus 1,1,100           ' RTU mode, Slave address = 1
' Enable the Ladder Logic scanner to copy data to and from the physical
' hardware and the Ladder/Modbus registers.
Set Ladder On
' Program should run forever without exiting

After this command, the Cubloc will respond to any incoming Modbus queries automatically. The Cubloc supports Modbus function codes 1, 2, 3, 4, 5, 6, 15, and 16.

Command Command Name
01, 02 Bit Read
03, 04 Word Write
05 1 Bit Write
06 1 Word Write
15 Multiple Bit Write
16 Multiple Word Write

The return interval is Cubloc's delay time for responding to the master Modbus device. If the return interval is set to be too fast, the master device might not be able to receive all data. The default setting is 1, which is about 200 micro-seconds. A value of 100 is about 4.5ms and a value of 255 is about 11ms.

Go CUBLOC home

cubloc/set_modbus/index.txt · Last modified: 2022/09/29 09:13 by COMFILE Technology