Hello,
I’m trying to access the registers of a modbus slave implemented in a CR1000, but after configuring every part, Modbus Master does not receive any answer to the polls(always shows timeout error).
My set-up is the next one:
(Modbus Master RTU) Device with RS485 port -------- (RS485) MD485 -(CS I/O port)- CR1000 (Modbus Slave)
The device with rs485 port can be a PLC or a PC with a USB/RS485 adapter (2 wires).
I’m using the ModBusSlave instruction as follows:
ModBusSlave( ComMe, 9600, 1, ModIn(), 0)
Parameters for MD485 are:
Active ports: CS I/O and rs485
Transparent mode
9600/8/n/1
I can access to both CR1000 and MD485 devices independently by using RS232, but I cannot access to CR1000 through MD485(even if I change the active ports in MD485).
Could someone guide me to get data accessible?
I’m not sure about which port to use in the ModBusSlave sentence (0/ComME/any SDC).
Best regards,
Vicente
The port that you specify in the ModBusSlave() instruction is going to depend upon the value of the [i]CS I/O Mode{/i] setting on the MD485. On principle, I would not recommend the use of the Modem Enable mode and instead would use SDC7, SDC8, SDC10, or SDC11. Regardless of your choice, the port parameter in the ModBusSlave() instruction must match the value specified in the MD485 setting.
The problem was just the port selected for CS I/O Mode. Now the system is properly working with ModBus communication.
Thanks for your help.
At the bottom of the http://www.canarysystems.com/canary-software-downloads.php page you can find a link to the CtrlTerm debug terminal, and on that page there is a Modbus example and a screen shot near the bottom of the page. I did that using a CR1000 as the slave. This might be useful for testing that a CR1000 is set up and working.
* Last updated by: PaulBreneman on 11/5/2013 @ 9:12 AM *