Datasheet

Section 15 Universal Serial Bus Interface (USB)
REJ09B0140-0900 Rev. 9.00 Page 575 of 846
Sep 16, 2010
H8S/2215 Group
(3) Automatic Stall by USB Function Module
When a stall setting is made with the Set Feature command, when the information of this module
differs from that returned to the host by the Get Descriptor, 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 EPnSTL, and returns a stall handshake (1-1 in figure 15.24).
Once an internal status bit is set, it remains set until cleared by a Clear Feature command from the
host, without regard to EPnSTL. After a bit is cleared by the Clear Feature command, EPnSTL is
referenced (3-1 in figure 15.24). 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 15.24). To clear a stall, therefore,
the internal status bit must be cleared with a Clear Feature command (3-1 in figure 15.24). If set
by the firmware, EPnSTL should also be cleared (2-1 in figure 15.24).