Mitsubishi Electric MELSEC Q Series Programming Manual page 606

APPENDICES
(4) Driver communication function
Driver communication function is only supported between servo amplifiers on the
same route starting from the Motion CPU until the last module.
Driver communication is not performed between servo amplifiers on different sub
routes, or between a servo amplifier connected on the main route after an optical
hub unit and a servo amplifier on a sub route connected to an optical hub unit.
When an axis set for driver communication is in a position where driver
communication cannot be performed, or when the connection of an axis set for
driver communication is not confirmed, all servo amplifiers including those that
are on axes not set to driver communication, cannot communicate with the
Motion CPU.
Routes where driver communication function is possible are shown below.
Within the main route
Within the same sub route
Between different sub routes
Between main route and sub route
(Between slaves on first optical hub unit (main route) and sub route)
Between main route and sub route
(Between slaves on later optical hub unit (main route) and sub route)
POINTS
Refer to "Q173D(S)CPU/Q172D(S)CPU Motion controller Programming Manual
(COMMON)" for details of "Driver communication function".
Route
: Driver communication
APP - 115
Supported
: No driver communication