Originally Posted by
JH870
The airbus XPDR ground logic means that mode S will be active regardless of auto/on. If you mean that ATC are requesting mode A (callsign only), then turning ALT RPTG to OFF will do this. With ALT RPTG off, altitude data is not reported.
Apparently it depends on the aircraft, in our CEOs according to FCOM if you have XPDR auto it will only transmit mode S on the ground but if you keep it ON it will not disable XPDR modes A & C on the ground, with our NEOs responding as you described; but for the OP it is not possible to disable XPDR Mode S without turning the whole XPDR to SBY, and they most likely are requesting you to just put XPDR to AUTO and TCAS to SBY so you still respond to Selective interrogation.