Subordinated debts question?

I need your help: debt B was subordinated to debt A. Debt A was rescheduled several times, and now installments to debt A are scheduled to be paid within the same period as the installments to debt B. If the cash flows allows it, can the company pay the installments to both debts, or all the installments to debt A must be repaid before any amount to debt B to be amortized? Were can I found more specific details on the net?