Datasheet

SAM9261 [DATASHEET]
Atmel-6062O-ATARM-SAM9261-Datasheet_21-Jun-16
710
than the minimum safe delay required above. If not, a software wait loop after RXSETUP clear may be added at
minimum cost
42.1.17 UHP
42.1.17.1 UHP: Non-ISO IN transfers
Conditions:
Consider the following sequence:
1. The Host controller issues an IN token.
2. The Device provides the IN data in a short packet.
3. The Host controller writes the received data to the system memory.
4. The Host controller is now supposed to carry out two Write transactions (TD status write and TD retirement
write) to the system memory in order to complete the status update.
5. The Host controller raises the request for the first write transaction. By the time the transaction is completed,
a frame boundary is crossed.
6. After completing the first write transaction, the Host controller skips the second write transaction.
Consequence: When this defect manifests itself, the Host controller re-attempts the same IN token.
Problem Fix/Workaround
This problem can be avoided if the system guarantees that the status update can be completed within the same
frame.
42.1.17.2 UHP: ISO OUT transfers
Conditions:
Consider the following sequence:
1. The Host controller sends an ISO OUT token after fetching 16 bytes of data from the system memory.
2. When the Host controller is sending the ISO OUT data, because of system latencies, remaining bytes of the
packet are not available. This results in a buffer underrun condition.
3. While there is an underrun condition, if the Host controller is in the process of bit-stuffing, it causes the Host
controller to hang.
Consequence: After the failure condition, the Host controller stops sending the SOF. This causes the connected
device to go into suspend state.
Problem Fix/Workaround
This problem can be avoided if the system can guarantee that no buffer underrun occurs during the transfer.
42.1.17.3 UHP: Remote Wakeup event
Conditions:
When a Remote Wakeup event occurs on a downstream port, the OHCI Host controller begins sending resume
signaling to the device. The Host controller is supposed to send this resume signaling for 20 ms. However, if the
driver sets the HcControl.HCFS into USBOPERATIONAL state during the resume event, then the Host controller
terminates sending the resume signal with an EOP to the device.
Consequence: If the Device does not recognize the resume (< 20 ms) event, then the Device will remain in
suspend state.
Problem Fix/Workaround
Host stack can do a port resume after it sets the HcControl.HCFS to USBOPERATIONAL.