HD6417660 RENESAS [Renesas Technology Corp], HD6417660 Datasheet - Page 642

• Manufacturer Part Number: HD6417660
• Description: Renesas 32-Bit RISC Microcomputer
• Manufacturer: RENESAS [Renesas Technology Corp]

20.6.3
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 the EPSTL register, and returns a stall handshake (1-1 in figure 20.18).
Once an internal status bit is set, it remains set until cleared by a Clear Feature command from the
host, without regard to the EPSTL register. After a bit is cleared by the Clear Feature command,
EPSTL is referenced (3-1 in figure 20.18). 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 20.18). To clear a stall, therefore,
the internal status bit must be cleared with a Clear Feature command (3-1 in figure 20.18). If set
by the application, EPSTL should also be cleared (2-1 in figure 20.18).
Rev. 1.00, 02/04, page 604 of 804
(1) Transition from normal operation to stall
(2) When transaction is performed when internal status bit is set, and Clear Feature is sent
(3) When Clear Feature is sent before transaction is performed
Automatic Stall by USB Function Module
(2-2)
(1-1)
(2-1)
(3-1)
STALL handshake
Transaction request
STALL handshake
Clear Feature command
Figure 20.18 Automatic Stall by USB Function Module
Internal status bit
Internal status bit
Internal status bit
Internal status bit
0 → 1
1 → 0
1
1
Normal status restored
Stall status maintained
To (2-1) or (3-1)
EPSTL
EPSTL
EPSTL
EPSTL
0
0
0
0
1. In case of USB
1. EPSTL cleared to 0
2. IN/OUT token
3. Internal status bit
4. EPSTL not
5. Internal status bit
1. Transmission of
1. Internal status bit
2. EPSTL not changed
specification
violation, etc., USB
function module
stalls endpoint
automatically
by application
received from host
already set to 1
referenced
not changed
STALL handshake
cleared to 0