SAM9260_14 Datasheet, PDF (750/784 Pages) ATMEL Corporation – AT91SAM ARM-based Embbedded MPU

43.1.15 Two-wire Interface (TWI)
43.1.15.1 TWI: Switch from Slave to Master Mode
At the end of transfer in slave mode, the slave mode is disabled, the master mode is enabled and thus a transfer in
master mode can be performed. In the current device, the start event is correctly generated but the SCL line is
stuck at 1, so no transfer is possible.
Problem Fix/Workaround
Two workarounds are possible:
1. Perform a software reset before going to master mode (TWI must be reconfigured).
or
2. Perform a slave read access before switching to master mode.
43.1.16 UHP
43.1.16.1 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 retire-
ment 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 com-
pleted, 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.
43.1.16.2 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.
SAM9260 [DATASHEET]
6221K–ATARM–15-Oct-12
750