SH7280 Datasheet, PDF (1394/1726 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine family

Section 25 USB Function Module
25.7.2 Automatic Stall by USB Function Module
When a stall setting is made with the Set Feature command, or in the event of a USB specification
violation, the USB function module automatically sets the internal status bit for the relevant
endpoint without regard to USBEPSTL register, and returns a stall handshake (1-1 in
figure 25.14).
Once an internal status bit is set, it remains set until cleared by a Clear Feature command from the
host, without regard to USBEPSTL register. After a bit is cleared by the Clear Feature command,
USBEPSTL is referenced (3-1 in figure 25.14). The USB function module continues to return a
stall handshake while the internal status bit is set, since the internal status bit is set even if a
transaction is executed for the corresponding endpoint (2-1 and 2-2 in figure 25.14). To clear a
stall, therefore, the internal status bit must be cleared with a Clear Feature command (3-1 in figure
25.14). If set by the application, USBEPSTL should also be cleared (2-1 in figure 25.14).
(1) Transition from normal operation to stall
(1-1)
STALL handshake
Internal status bit
0→1
USBEPSTL
0
To (2-1) or (3-1)
1. In case of USB
specification
violation, etc., USB
function module
stalls endpoint
automatically
(2) When transaction is performed when internal status bit is set, and Clear Feature is sent
(2-1)
Transaction request
Internal status bit
1
(2-2)
USBEPSTL
0
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
STALL handshake
Internal status bit
1
USBEPSTL
0
1. Transmission of
STALL handshake
Stall status maintained
(3) When Clear Feature is sent before transaction is performed
(3-1)
Clear Feature command
Internal status bit
1→0
USBEPSTL
0
Normal status restored
1. Internal status bit
cleared to 0
2. USBEPSTL not
changed
Figure 25.14 Automatic Stall by USB Function Module
Rev. 1.00 Jun. 26, 2008 Page 1364 of 1692
REJ09B0393-0100