NEC Network Controller uPD98502 - Manual (Page 358)

CHAPTER 6 USB CONTROLLER
358 Preliminary User’s Manual S15543EJ1V0UM
6.6.7 Detection of errors on USB
USB Controller has some functions which detect some errors on the USB.
Errors shown in figure below are related to Isochronous EndPoint and SOF packet.
Figure 6-24. USB Timing Errors
SOF
SOF
ISO.
ISO.
SOF
ISO.
SOF
ISO.
SOF
ISO.
Correct
Loss of
Data
Loss of
SOF
Extra
Data
Extra
SOF
Error
Error
Error
Error
(1) If “Loss of Data” error has occurred, EP2ND bit (Bit 5) in USB General Status Register 2 will be set. The other
action of USB Controller for this error is explained in next section (Section 6.6.8).
(2) If “Loss of SOF” error has occurred, SL bit (Bit 0) in USB General Status Register 2 will be set.
In this case, USB Controller only reflect the error to USB General Status Register.
(3) If “Extra Data” error has occurred, EP2ED bit (Bit 6) in USB General Status Register 2 will be set.
In this case, USB Controller only reflect the error to USB General Status Register.
(4) If “Extra SOF” error has occurred, ES bit (Bit 1) in USB General Status Register 2 will be set.
In this case, USB Controller only reflect the error to USB General Status Register.
USB Controller can detect the other Error listed below.
• Isochronous data oversize error: If received data packet size is over Max Packet Size of
EndPoint2, USB Controller will set EP2OS bit (Bit 7) in USB
General Status Register 2.
• Incorrect EndPoint Number:
If received IN/OUT TOKEN packet includes the EndPoint
Number which is not enabled by V R 4120A or which is over 7,
USB Controller will set IEA bit (Bit 19) in USB General Status
Register 2.
• No data in EndPoint1 Tx FIFO:
If IN TOKEN packet for EndPoint2 comes when Tx FIFO for
EndPoint2 is not ready, USB Controller will not transmit any