Прямого запрета в ДШ нет, попробуй. Регистры PDC проинициализируй: PDC Receive Pointer/Counter Register, PDC Transmit Pointer/Counter Register на соответствующие адреса RAM и PDC Transfer Control Register (+)
Из ДШ на AT91SAM7Sxx: Each peripheral is connected to the PDC by a receiver data channel and a transmitter data channel. Each channel has an internal 32-bit memory pointer. Each memory pointer points to a location anywhere in the memory space (on-chip memory or external bus interface memory).