Hi, all.

Please help me resolve the dispute between the engineers.
The essence of the dispute: module Sm-421 (6ES7421-1BL01-0AA0) the role of terminals 12-14, 23-26, 35-38?
Group 1 claims that these terminals are not connected anywhere and it is not necessary to connect DC minus to any of them. As proof, they show page 92 of the "S7-400 Automation System Module Data Reference Manual, 04/2023, A5E00850736-AL". The only negative connection point is terminal 48.
Group 2 states that these terminals represent the terminals of the reference potential M (0 V) for the corresponding groups of digital inputs. And the diagram on page 92 is simplified. Therefore, the negative DC must be connected to terminals 12, 23, 35 and 48.

Please confirm that one of the groups is correct.