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Section 20 USB Function Module
Rev. 4.00 Sep. 14, 2005 Page 781 of 982
REJ09B0023-0400
(1) Transition from normal operation to stall
(1-1)
Transaction request
USB
Reference
(1-2)
STALL handshake
Stall
To (2-1) or (3-1)
Normal status restored
(1-3)
(2) When Clear Feature is sent after USBEPSTL is cleared
(2-1)
STALL handshake
Transaction request
(2-2)
Clear Feature command
Clear Feature command
(2-3)
(3) When Clear Feature is sent before USBEPSTL is cleared to 0
(3-1)
1. 1 written to
USBEPSTL by
application
1. IN/OUT token
received from host
2. USBEPSTL
referenced
1. Transmission of
STALL handshake
1. Internal status bit
cleared to 0
1. Internal status bit
cleared to 0
2. USBEPSTL not
changed
1. 1 set in USBEPSTL
2. Internal status bit
set to 1
3. Transmission of
STALL handshake
1. USBEPSTL cleared
to 0 by application
2. IN/OUT token
received from host
3. Internal status bit
already set to 1
4. USBEPSTL not
referenced
5. Internal status bit
not changed
To (1-2)
Internal status bit
0
USBEPSTL
0 → 1
Internal status bit
0
USBEPSTL
1
Internal status bit
0 → 1
USBEPSTL
1
Internal status bit
1
USBEPSTL
1 → 0
Internal status bit
1
USBEPSTL
0
Internal status bit
1 → 0
USBEPSTL
0
Internal status bit
1 → 0
USBEPSTL
1
Figure 20.13 Forcible Stall by Application