SH7720 Datasheet, PDF (863/1524 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series

Section 24 USB Host Controller (USBH)
24.7 Usage Notes
1. When using the USB host controller, the bus clock (Bφ) must be set to 32 MHz or higher. The
peripheral clock (Pφ) must also be set to a higher frequency than 13 MHz.
2. Usage notes on Resume operation
(1) Phenomenon
While the USB host is providing an output of a Resume (*1) signal, suppose that (a)
PortPower is turned off or that (b) OverCurrent is produced. In this case, the Resume signal
should ordinarily be stopped so that the idle (*2) state will be established. Actually,
however, the result is that an idle signal is output.
*1: In FullSpeed, D+ = Low and D- = High. In LowSpeed, D+ = High and D- = Low.
*2: In FullSpeed, D+ = High and D- = Low. In LowSpeed, D+ = Low and D- = High.
(2) Conditions when the above phenomenon occurs
While a Resume (*1) signal is being output, (a) PortPower is turned off or (b) OverCurrent
is produced.
(3) Conditions when the above phenomenon does not occur
The above phenomenon will not occur if there is no Resume operation, that is, Suspend
operation has not been done.
(4) Problem avoidance by software
If the above phenomenon occurs, Resume is interrupted and then an idle signal is output.
However, turning on PortPower enables device recognition. The above phenomenon is
removed by the subsequent Port Reset for the device. Normal operation is thus recovered.
Note, however, the above phenomenon will not be removed by USB Reset, which is
generated by the HCFS1 and HCFS0 bits in the Hc Control (USBHC) register. For this
reason, if you are using software that issues USB Reset by the HCFS1 and HCFS0 bits in
the Hc Control (USBHC) register, modify the software so that it issues USB Reset (Port
Reset) by setting the PRS bit in the Hc Rh Port Status 1 or Hc Rh Port Status 2
(USBHRPS1 or USBHRPS2) register.
However, there is no need to take corrective action if Port Rest has already been issued by
the PRS bit before the recognition of USB device connection.
Rev. 3.00 Jan. 18, 2008 Page 801 of 1458
REJ09B0033-0300