
Chapter 2. Endpoint Zero Page 2-11
3. Restore the stalled endpoint to its default condition, ready to send or accept data after the stall
condition is removed by the host (via a
Clear Feature/Stall
request). For EP1 IN, for example,
firmware should clear the BUSY bit in the EP1CS register; for EP1OUT, firmware should load
any value into the EP1 byte-count register.
4. Clear the HSNAK bit in the EP0CS register (by writing 1 to it) to terminate the Set Feature/Stall
CONTROL transfer.
Step 3 is also required whenever the host sends a Set Interface request.
2.3.3 Clear Feature
Clear Feature
is used to disable remote wakeup or to clear a stalled endpoint.
Data Toggles
The FX2 automatically maintains the endpoint toggle bits to ensure data integrity for USB
transfers. Firmware should directly manipulate these bits only for a very limited set of circum-
stances:
• Set Feature/Stall
• Set Configuration
• Set Interface
Table 2-8. Clear Feature-Device (Clear Remote Wakeup Bit)
Byte Field Value Meaning Firmware Response
0 bmRequestType
0x00
OUT, Device
Clear the remote wakeup bit.
1 bRequest
0x01
“Clear Feature”
2wValueL
0x01
Feature Selector:
3 wValueH 0x00 Remote Wakeup
4 wIndexL 0x00
5 wIndexH 0x00
6 wLengthL 0x00
7 wLengthH 0x00
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