![](http://datasheet.mmic.net.cn/30000/MQ83C154DXXX-25-883R_datasheet_2377229/MQ83C154DXXX-25-883R_816.png)
816
6384E–ATARM–05-Feb-10
AT91SAM9G20
44.3.11
Two-wire Interface (TWI)
44.3.11.1
TWI: RXRDY Flag is not reset by a SOFTWARE Reset
The RXRDY Flag is not reset when a Software reset is performed.
Problem Fix/Workaround
After a Software Reset, the Register TWI_RHR must be read.
44.3.12
UHP
44.3.12.1
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 error occurs, the Host controller tries the same IN token again.
Problem Fix/Workaround
This problem can be avoided if the system guarantees that the status update can be completed
within the same frame.
44.3.12.2
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-stuff-
ing, 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.