SH7727 Datasheet, PDF (832/1109 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7700 Series

Section 24 USB HOST Module
24.5.3 Restrictions when a Low-Speed Device is Disconnected
When a low-speed device connected to the root port is disconnected while the data is transmitted
to the host, this USB controller might hung. Therefore, be sure not to disconnect the low-speed
device while the data is transmitted. If that disconnection is detected, reset USB (write 00 to the
HCFS bit in the HcControl register).
24.6 Restrictions on the Software Reset and USB Reset
The operation of the controller might become stuck if a software reset (1 written to the HCR bit in
the HcCommandStatus register) or USB reset (00 written to the HCFS bit in the HcControl
register) is performed while the USB host controller is carrying out a master memory write.
Master memory write operations are performed at the start of frame (SOF) and during data
transfer. To prevent the host controller from becoming stuck, use one of the following methods:
1. Write the program so that the SDF timing is derived from the HcFmRemaining value and a
software reset or USB reset is applied around the middle of a frame in which all list processing
is disabled.
2. If you issue a reset for the USBH module after applying a software reset or USB reset, no stack
will occur. (Set the module software reset register (SRSTR).)
24.7 Notes on Using USB Host with Versions Previous to the SH7727C
The USB host controller of the SH7727 and SH7727B may erroneously recognize an SE0 state
during data transfer. As a result, the controller incorrectly detects a device not connected state
(erroneous device not connected detection) even though the device actually is connected. The
following methods may be used to work around this problem.
1. Use the low speed (1.5 Mbps) mode. Erroneous device not connected detection does not occur
during low speed data transfer.
2. When using the full speed (12 Mbps) mode, use method (a) or (b) below to avoid erroneous
device not connected detection.
a. Ensure that the D+, D– crossover voltage output by the USB function device exceeds
SH7727 AVcc_USB × 0.55 (V).
b. Ensure that received data strings do not contain more than 28 consecutive 0 bits.
Note: The prohibition on consecutive 0 bits applies to all bits of SYNC + PID + DATA +
CRC16 + EOP. EOP is counted as 2 bits.
Rev. 5.00 Dec 12, 2005 page 760 of 1034
REJ09B0254-0500