(snip)
How many Modbus TCP connection can a CPU 1513-1 PN have towards Modbus TCP servers in parallel?
It will be 2-3 signal per connection.

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Split from NMEA seriell output.

Check this link

https://support.industry.siemens.com/tf/WW/en/posts/number-of-modbus-tcp-ip-devices-on-s7-1500-cpu-1515-2pn-will-support/161505?page=0&pageSize=10

You might find the answer there.

Is there any reason you want to use a S7?

Best Regards.

What do you mean with S7?

These will be a control system with a interface toward third parties.

I cannot find the answear there, links further talking about PLC as server, these is not the case here.

The third party is the server (slave) and the PLC shall be client (master).

I have talked with Siemens.

1513-1 has 88 connection resources. 10 is reserve to PG, HMI and WEB.

78 is left to use for Modbus TCP or S7 etc.... so then I have plenty :)

only need around 10.