USB on-the-go high-speed (OTG_HS)
RM0090
1522/1731
DocID018909 Rev 11
1.
Disable the IN endpoint to be stalled. Set the STALL bit as well.
2. EPDIS = 1 in OTG_HS_DIEPCTLx, when the endpoint is already enabled
–
STALL = 1 in OTG_HS_DIEPCTLx
–
The STALL bit always takes precedence over the NAK bit
3. Assertion of the Endpoint Disabled interrupt (in OTG_HS_DIEPINTx) indicates to the
application that the core has disabled the specified endpoint.
4. The application must flush the nonperiodic or periodic transmit FIFO, depending on the
endpoint type. In case of a nonperiodic endpoint, the application must re-enable the
other nonperiodic endpoints that do not need to be stalled, to transmit data.
5. Whenever the application is ready to end the STALL handshake for the endpoint, the
STALL bit must be cleared in OTG_HS_DIEPCTLx.
6. If the application sets or clears a STALL bit for an endpoint due to a
SetFeature.Endpoint Halt command or ClearFeature.Endpoint Halt command, the
STALL bit must be set or cleared before the application sets up the Status stage
transfer on the control endpoint.
Special case: stalling the control OUT endpoint
The core must stall IN/OUT tokens if, during the data stage of a control transfer, the host
sends more IN/OUT tokens than are specified in the SETUP packet. In this case, the
application must enable the ITTXFE interrupt in OTG_HS_DIEPINTx and the OTEPDIS
interrupt in OTG_HS_DOEPINTx during the data stage of the control transfer, after the core
has transferred the amount of data specified in the SETUP packet. Then, when the
application receives this interrupt, it must set the STALL bit in the corresponding endpoint
control register, and clear this interrupt.
35.13.8 Worst case response time
When the OTG_HS controller acts as a device, there is a worst case response time for any
tokens that follow an isochronous OUT. This worst case response time depends on the AHB
clock frequency.
The core registers are in the AHB domain, and the core does not accept another token
before updating these register values. The worst case is for any token following an
isochronous OUT, because for an isochronous transaction, there is no handshake and the
next token could come sooner. This worst case value is 7 PHY clocks when the AHB clock
is the same as the PHY clock. When the AHB clock is faster, this value is smaller.
If this worst case condition occurs, the core responds to bulk/interrupt tokens with a NAK
and drops isochronous and SETUP tokens. The host interprets this as a timeout condition
for SETUP and retries the SETUP packet. For isochronous transfers, the Incomplete
isochronous IN transfer interrupt (IISOIXFR) and Incomplete isochronous OUT transfer
interrupt (IISOOXFR) inform the application that isochronous IN/OUT packets were
dropped.
Choosing the value of TRDT in OTG_HS_GUSBCFG
The value in TRDT (OTG_HS_GUSBCFG) is the time it takes for the MAC, in terms of PHY
clocks after it has received an IN token, to get the FIFO status, and thus the first data from
the PFC block. This time involves the synchronization delay between the PHY and AHB
clocks. The worst case delay for this is when the AHB clock is the same as the PHY clock.
In this case, the delay is 5 clocks.