h8s-2172 Renesas Electronics Corporation., h8s-2172 Datasheet - Page 389

• Manufacturer Part Number: h8s-2172
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family H8s-2100 Series
• Manufacturer: Renesas Electronics Corporation.

2. Automatic Stall by USB Function Module
(1) Transition from normal operation to stall
(2) When transaction is performed while internal status bit is set
(3) When Clear Feature is sent before transaction is performed
When a stall setting is made with the Set Feature request or in the event of a USB specification
violation, the USB module automatically sets the internal status bit for the corresponding
endpoint without regarding to EPSTL0, and returns a stall handshake (1-1 in figure 12.14).
Once an internal status bit is set, it remains set until cleared by a Clear Feature request from
the host, without regarding to EPSTL0. After a corresponding bit is cleared by the Clear
Feature request, EPSTL0 is referred (3-1 in figure 12.14). The USB 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 12.14). To clear a
stall, therefore, the internal status bit must be cleared with a Clear Feature request (3-1 in
figure 12.14). If set by the firmware, EPSTL0 should also be cleared (2-1 in figure 12.14).
(2-2)
(3-1)
Stall handshake
Transaction request
Stall handshake
Clear Feature command
(1-1)
(2-1)
Figure 12.14 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
USB function module
To (2-1) or (3-1)
EPSTL0
EPSTL0
EPSTL0
EPSTL0
0
0
0
0
Rev. 2.00, 03/04, page 357 of 534
1. In case of USB
1. Clear EPSTL0 to 0 by
2. Receive IN/OUT
3. Internal status bit has
4. EPSTL0 is not
5. No change in internal
1. Transmit stall
1. Clear the internal
2. No change in
specification violation,
USB function module
stalls endpoint
automatically.
firmware
token from the host
been set to 1
referred to
status bit
handshake
status bit to 0
EPSTL0