28.3.3 SRAM Memory Mapping

The USB peripheral uses the device’s internal SRAM to store:
  • Transaction Complete FIFO
  • Endpoint Configuration Table
  • USB Frame Number

The Endpoint Configuration Table Pointer (USB.EPPTR) register is used to set the SRAM address for the endpoint configuration table. The USB frame number (FRAMENUM) register and the transaction complete (FIFO) table locations are derived from this. The location is selectable inside the device’s internal SRAM. The figure below gives the relative memory location of each area.

Figure 28-9. USB Memory Mapping (Descriptor table, FIFO, frame number, endpoint buffers) In RAM