NOC Card - Modbus TCP Polling Unstable Data

[RuchirSomani]

We are facing below challenge while using NOC card 0301.2

1. Using READ_VAR block, not at single Modbus TCP request is getting generated.

    

2. When we used default Modbus TCP feature for NOC card, till the 1^st request all the activity runs smoothly. As soon as we generate 2^nd request, all the MFM data in M580 goes haywire. Please find attached videos for reference.

Please suggest proper solution for this problem as we have to use 14 Nos. of request with each request having data polling of approx. 120 Nos. of 16 bit registers.

[Trinxs1]

How are you triggering the read activity as it seems every second read is OK, but you are zeroing the data in between. 

What are you reading from?  is it a serial gateway?

Have you raised the issue with your technical support team?

[RuchirSomani]

Hi,

1. Yes we are reading all the request every 1 second.

2. We have selected option of ZEROING the last value - considering it shall set the parameters value to ZERO if any device goes offline or query goes unresponsive.
Is it because of this setting that the values are intermittently going to ZERO ??

3. We are reading the value for Modbus Serial to TCP Gateway device.

[YONGHO-KIM]

1. Please try reading Modbus TCP data using the READ_VAR block.

1. Refer to the attached example below.
2. If you have any questions regarding the configuration, feel free to ask.
3. The example configuration is as follows:

• Target IP: 172.168.12.101
• Target Address: 1
• Reads 96 registers starting from address 3000, and 32 registers starting from address 3096, using Holding Registers.
•   

[RoozeeR]

Hello Ruchir,

As you are reading from a Modbus device using a gateway in between you must make sure that your gateway is able to handle multiple (2 in your case now) Modbus TCP messages at the same time.

Also the IO-scanning functionality uses a relative fast retry mechanism. Specially when the gateway modbus device doesn't respond fast enough (it's baudrate is limited, not 100MB), it will cause retry's to be sent out before the gateway was even ready to respond,specially having more than 1 message to be sent/answered. You can try using the Gateway/Bridge device checkbox, but this is only available when you define the NOC card as type BMENOC301.4 (instead of .2). 

Note the 301.4 is the same hardware as 301.2, only check the firmware which must be >=2.11.

If that doesn't solve your issue use READ_VAR function blocks.