NEC uPD98502 Buffer Dire ctory

CHAPTER 6 USB CONTROLLER
Preliminary User’s Manual S15543EJ1V0UM 361
Figure 6-25. Example of Buffers Including Corrupted Data
Buffer descriptor
Buffer descriptor
Buffer descriptor
Valid
Data
Valid
Data
Valid
Data
Valid
Data
Link pointer
Buffer descriptor
Valid
Buffer desc.(L=1)
Corrupted
Data
Corrupted
Data
Buffer descriptor
Link pointer Valid
Data
Buffer Dire ctory
Valid
Corrupted
Data Max Packet Size
Max Packet Size
6.6.9 Rx FIFO overrun
On Isochronous Rx EndPoint (EP2), if data reading from Rx FIFO is delayed by some problem, Rx FIFO Overrun
will occur.
In the case of corruption, action of USB Controller varies according to Rx Mode.
(a) Rx normal mode
USB Controller sets EP2FO (EndPoint2 No Data) bit (Bit 9) in USB General Status Register 2.
USB Controller writes the Rx indications which indicates that EP2 FIFO Overrun has occurred.
USB Controller doesn’t write any dummy data to Data Buffer on system memory.