Hi pawelkasprzak

a one page overview that lists number of I/O Devices per CPU and/or CM/CP would be a great, but I am not aware of its existence.

The tech spec of each CPU will give you this info though and it is for example 128 for a 1512SP F-1 PN CPU and 512/128 respectively for the two on-board Interfaces of a 1518-4 PN/DP CPU.

Note though that the number of I/O devices with prioritized startup is generally lower and the same applies for number IRT I/O Devices (in case you want to use these features).

In case you are planning of connecting DP Slaves to the Profinet via an IE/PB Link, be aware too that you must include each DP Slave in the Profinet I/O Device count.