SH7720 Datasheet, PDF (846/1524 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series

Section 24 USB Host Controller (USBH)
24.3.16 Hc Fm Number b Register (USBHFN)
USBHFN is a 16-bit counter. It indicates the reference of timing between events occurring in the
host controller and host controller driver. The host controller driver uses a 16-bit value specified in
this register and generates a 32-bit frame number without necessity for a frequent access to the
register.
Initial
Bit
Bit Name Value R/W Description
31 to 16 
All 0 R Reserved
These bits are always read as 0. The write value should
always be 0.
15 to 0 FN15 to FN0 All 0 R/W Frame Number
These bits are incremented when USBHFN is reloaded.
The count will return to H'0 after H'FFFF. When the host
controller transits to the UsbOperational state, these bits
are automatically incremented. After the host controller
increments the FN bit and sends SOF in each frame
boundary, the content is written to HCCA before the host
controller reads first ED in the frame. After writing to
HCCA, the host controller sets the SF bit in USBHIS.
Rev. 3.00 Jan. 18, 2008 Page 784 of 1458
REJ09B0033-0300