Fujitsu F2MC-16LX Hardware Manual page 306

CHAPTER 13 USB FUNCTION
[bit 8, bit 7] Reserved bit
These bits are reserved bits. Writing has no effect on the operation. Reading is indeterminate.
[bit 6 to bit 0] SIZE: Packet size display bit
When OUT packets have been transferred from EP0, the number of data bytes that has been written into
the receive buffer is displayed. The SIZE bit is updated to a valid value when the interrupt factor for
DRQO in the EP0O status register (EP0OS) has been set.
<Example> 8 bytes→"08
290
", 64 bytes→"40 " (maximum value)
H H