Modbus TCP communication

[felipealencr]

Hi folks,

I have a Controllogix in communication with a zigbee coordinator using Logix AIO for modbus tcp. This zigbee coordinator have 3 slaves IO, but when I turn off one of those IO the coordinator hold the last input information and flag a timeout status and the status of input in PLC stay hold. Can I see this timeout flag in PLC monitor using the add on instruction, for each IO for example?

 

[jape]

In the AOI block for the client you have some diagnostic tools for each client the AB PLC is connected to. In that senario you would be able to tell if you are getting a reply from the device

*Diagnostic.TransLastError* should probably return something you could work with but by monitoring the diagnostics when you disconnect the device you should see what you can reliably use.

If your Zigbee coordinator is a master and your 3 zigbee devices are connected to that and you are disconnecting one of them then you will not be abe to see that they are not responding in the AOI as the master will still be responding with their last known values. In this case you could either look in your zigbee modbus table for a tag that will tell you if your slaves aren't connected or you could monitor a parameter from the slave that you know will be continuously changing and if you do not see it change in the appropraite ammount of time than flag a comm error.

If your zigbee devices are responding through your master and using the master as a relay than you should be able to raise a response from it in the same manner as 1 but since they all use the same comm port you will need to monitor them in software to coorelate the failed messages with the device in question.

 

[Contr_Conn]

Can you post Zigbee device manual here?
If device is still responding with IO module off, then it should be a status register with some Modbus address indicating this and the AOI should be able to read it.

 

[felipealencr]

Can you post Zigbee device manual here?
If device is still responding with IO module off, then it should be a status register with some Modbus address indicating this and the AOI should be able to read it.

Coordinator:

https://www.icpdas.com/web/product/download/wireless/zigbee/concentrator/mdc-211-zt/document/manual/MDC-211-ZT_usermanual_en.pdf

Zigbee IO:

http://ftp.icpdas.com/pub/cd/usbcd/napdos/ZigBee/zt_series/document/zt_dio/zt-2000_dio_usermanual_0121_en.pdf

 

[Contr_Conn]

It looks like for each device reading registers starting 39600 can tell you if devices are responding or not.
In the AOI it will be command 4, Address 9599

 

[felipealencr]

can i'm monitor this command 4 on the AOI Transaction word?

 

[Contr_Conn]

Use TransactionType = 4, BeginAddress = 3599, Count =1

 

[felipealencr]

Thanks!
For this coordinator I used the BeginAddress = 9600 (decimal) and Count = 3 in Transaction [1], because I have 3 IOs. Now I can read the inputs and the registers timeout.
The great detail is understand what is the BeginAddress, and this is the address in remote device.

 

[Contr_Conn]

You need to check your code: to address Input Register 39600 in the AOI, you must use 9599 as a BeginAddress
Using 9600 will be reading register 39601 - welcome to the "Shift by 1" world of Modbus

 

[felipealencr]

You need to check your code: to address Input Register 39600 in the AOI, you must use 9599 as a BeginAddress
Using 9600 will be reading register 39601 - welcome to the "Shift by 1" world of Modbus

When I use 9599 like BeginAddress the transaction results in a exception -1, I don´t know why, but I think it's a configuration on Zigbee coordinator. With 9600 it's works and I tested it by turning off each of the 3 IOs.
Exemple: it turning off the third IO

 

[Contr_Conn]

Then it looks like manual error.