Toshiba H1 Series Data Book page 479

3. When generating toggle error of device controller
a. UDC operation
If USB host fail to receive ACK transmitted from UDC in OUT transfer, USB
host transmits the same data to UDC again. When the FIFO is available to receive,
UDC detects toggle error because of detecting the same data(having the same
toggle as the data which is received just before) and returns ACK. UDC rejects it
because the data have already received normally. While, if FIFO is not available,
UDC returns NAK and informs USB host that is unable to receive.
If using USB device controller in TMP92CZ26A, the crystal oscillator (USB standard ≤
4.
10 MHz±2500ppm) is recommended. And in this case, the stage of external hub can be
used until max 3 stages by the precision of this USB device controller and the internal
clock. If USB compliance (USB logo) is needed, the 5 stages connection is needed for
external hub. And it is needed that input 48MHz clock from X1USB pin (USB standard
≤ ±2500ppm.)
92CZ26A-476
TMP92CZ26A