M580 Modbus TCP Client Q&A

[ANF-Energy]

Thanks to Lt. Commander RooseR for his assistance in setting up Modbus TCP client in another post.

My manager now has two follow up questions and we use the BMEH582040:

1) Does the IO Scanner run independently of the software tasks? 

2) Is there a limit to the number of devices the IO Scanner can poll?

For the second question, the Modicon M580 Hardware Reference Manual states the BMEH582040 can have a maximum of 64 "distributed devices" but we want to confirm that is max number for the IO scanner, not an overall device number including other type of communication. 

[HAIBO]

Hello Andrew,

1,Each ioscaner runs independently 

2,The BMEH582040 can have a maximum of 64 "distributed devices"  and it means it could support 64 ioscanings. This information could also be found in summary of CPU DTM device list 

[ciupol]

---

@ANF-Energy wrote:

For the second question, the Modicon M580 Hardware Reference Manual states the BMEH582040 can have a maximum of 64 "distributed devices" but we want to confirm that is max number for the IO scanner, not an overall device number including other type of communication. 

---

This 64 device limit is not only for IO scanner. If you configure Ethernet/IP devices or HART modules those will increase the number of used devices. Basically everything you add in DTM browser is a device.

If you do any data exchange using communication blocks (for example READ_VAR or DATA_EXCH) those do not count towards the DIO device limit (but have some other restrictions).

Also keep in mind that there is a limited number of connections (64 in your case). If you configure two request for single DIO device there will be one device but two connections used.