Foxmoth,
I'm not sure you did get it right, if the one didn't receive step-confirmation from other (e.g not working TCAS at all) no RA provided, TA only mode available (any TCAS guru around, correct me if I wrong). And my last note remains: you should LISTEN other traffic commands too.
TCAS2000 Brochure (PDF)
but not in full details, sorry
(please don't take it as advertising)