How can an AS-i input bit be linked to a digital input bit?

Answer:

Let us assume that the digital input signal is on input E5.

The AS-i input bits can be linked to a digital output:

=> L-C0415 / 1 (A1) selection 37-39 (AS-i D0-D2)
the digital output can be connected to a digital input (example: jumper A1 - E4).
using code L-C0409/4 (digital link E4) selection 1, E4 has only high level if E4 and E5 have high level.
the input E4 is now 'connected in series' with an AS-i bit and a digital input.