Panel server PAS600 Maximum Modbus devices possible

[lalitlambole03]

Hello Folks, 

I am using PASS600 as Modbus RTU to TCP/IP converter and trying to connect 16 serial devices at 9600 bps and 500ms polling period on Modbus RTU protocol but there seems to be some issue with this connection. Can anyone please provide clarity on exact number of devices which can be connected in single loop with this setting for PAS600 panel server.

[Guillaume_Evrard]

hello @lalitlambole03 

You have to make your own computations taking into account polling cycle, baudrate, nb of devices polled, answer time, time to revert the RS485 communication and 10ms delay by PAS . Pay attention to the timeout on the PAS (Time it will wait before returning no answer from device if devices are slow). 

Or add one by one and check performance. remember the limit from release note in terms of devices

Do not configure the devices in the PAS, use the transparent gateway feature.

Kind Regards

[Romain_Polette]

Hello @lalitlambole03 , 

16 serial devices connected to Panel Server and poll frequency @ 9600 Bds seems "comfortable". 

Communication issues on serial bus can have many different root causes:

1. bad quality wiring of the bus (shield continuity, ground reference, polarization, termination resistor)
2. Modbus stack of your serial devices (low Modbus performances, response time)
3. Modbus frames sent by your Modbus Master (too many consecutive registers not managed by serial devices, bad addressing)
4. Serial line parameters (settings not aligned between gateway and serial devices, gateway and Modbus Master timeout) 

To better understand your issue:

• Do you have any Modbus exception displayed on your Master ?
• Can you poll the serial devices directly from the PAS600 interface ? Settings > Modbus devices > Modbus registers read
• Is this working with only 1 or less than 10 devices ?
• Did you activate Modbus TCP services on PAS600 ?

Regards, 

[lalitlambole03]

Thank you I will try adding them one by one using transparent gateway

[lalitlambole03]

Yes TCP/IP is enabled, and individual devices can be polled also the loop is working fine for less than 10 devices in loop.