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USB Device Controller
Successful completion of non-autodecoded control read transfers is indicated
by the host sending an OUT token followed by an empty packet and the USB
device controller responding with ACK. If the data packet sent by the USB host
during the status stage of a control read request is not empty, the OUT
transaction is accepted by the core, but OUT data is not put into the endpoint
0 RX FIFO. If the status packet has a DATA0 PID instead of a DATA1 PID, a
STALLed is returned by the core and an interrupt is asserted.
Non-Autodecoded Control Read Transfer Error Conditions
If an error occurs while dealing with the control read, which the MPU cannot
deal with itself, it must signal STALL to the USB host for all subsequent
transactions until a new setup token to endpoint 0 occurs. This is true for both
data stage and status stage transactions. This is most conveniently done by
setting endpoint 0 SYSCON2.STALL_CMD bit, which causes stalling of all the
remaining transactions of all remaining stages of a non-autodecoded control
transfer, up to the reception of the next valid SETUP command.
Error conditions are handled as for BULK/INTERRUPT transactions. The USB
device controller module responds to control read status stage transactions
that have a bad token or bad data by not sending a handshake packet. In both
cases, the transaction is ignored and no general USB interrupt is generated
to the MPU.
SPRU761A
Universal Serial Bus (USB)
133
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