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UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
572 of 1269
NXP Semiconductors
UM10503
Chapter 23: LPC43xx USB0 Host/Device/OTG controller
23.10.8.3 Status phase
Similar to the data phase, the DCD must create a transfer descriptor (with byte length
equal zero) and prime the endpoint for the status phase. The DCD must also perform the
same checks of the ENDPTSETUPSTAT as described above in the data phase.
Remark:
The MULT field in the dQH must be set to “00” for bulk, interrupt, and control
endpoints.
Remark:
Error handling of status phase packets is the same as bulk packets described
previously.
23.10.8.4 Control endpoint bus response matrix
Shown in the following table is the device controller response to packets on a control
endpoint according to the device controller state.
[1]
BS error = Force Bit Stuff Error
[2]
NYET/ACK – NYET unless the Transfer Descriptor has packets remaining according to the USB variable
length protocol then ACK.
[3]
SYSERR – System error should never occur when the latency FIFOs are correctly sized and the DCD is
responsive.
23.10.9 Isochronous endpoint operational model
Isochronous endpoints are used for real-time scheduled delivery of data, and their
operational model is significantly different from the host throttled Bulk, Interrupt, and
Control data pipes. Real time delivery by the device controller is accomplished by the
following:
•
Exactly MULT Packets per (micro) Frame are transmitted/received. Note: MULT is a
two-bit field in the device Queue Head. The variable length packet protocol is not
used on isochronous endpoints.
•
NAK responses are not used. Instead, zero length packets are sent in response to an
IN request to an unprimed endpoint. For unprimed RX endpoints, the response to an
OUT transaction is to ignore the packet within the device controller.
•
Prime requests always schedule the transfer described in the dTD for the next (micro)
frame. If the ISO-dTD is still active after that frame, then the ISO-dTD will be held
ready until executed or canceled by the DCD.
Table 445. Control endpoint bus response matrix
Token
type
Endpoint state
Setup
lockout
STALL
Not primed Primed
Underflow
Overflow
Setup
ACK
ACK
ACK
n/a
SYSERR
-
In
STALL
NAK
Transmit
BS error
n/a
n/a
Out
STALL
NAK
Receive and
NYET/ACK
n/a
NAK
n/a
Ping
STALL
NAK
ACK
n/a
n/a
n/a
Invalid
Ignore
Ignore
Ignore
Ignore
Ignore
ignore