M172 Modbus serial master

[POPE3909]

Hi Guys,

I'm trying to read modbus registers with M172 as a master by following the below instructions:

Training M172 - M9.3 Modbus Serial Master - YouTube

I am getting '2' as output which is not part of what is described in object properties. I tried clicking the function block in case it shows the source code but no luck.

What does '2' means in this case? Could you please provide a direction where I can find more information?

Thank You.

[Bastian_Schmitz · Accepted solution]

Hi,

I´m not sure but I expect this is a illegal address error. Did you try to increase/decrease the start address with 1?

[LeTomas]

Hi @POPE3909 ,

If we follow the object properties for the "sysMbMTCP_FCxx" it looks like that the number 2 means "Exception code illegal data address" but i am not 100% sure if it is that in your case.

Best regards,

LeTomas

[POPE3909]

Hi Guys,

Thank for your replies. Yes, I was reading the incorrect address. I changed to the correct address and it is all good now. 

But I still want to know where/how to check the object properties? In the software, it only shows the following:

No mention of '2'?

[LeTomas]

Hi @POPE3909 ,

I just checked the other blocks from ModbusTCP instead of serial:

BR

LeTomas

[Bastian_Schmitz]

Hi Pope3909,

it seems there is space to increase the detail on the description.

The response which is fully described on the newer Modbus TCP functions is identical to the standart modbus response which you could find here Link

[POPE3909]

Thanks guys. 🙏