SH7205 Datasheet, PDF (1266/1904 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7200 Series

Section 24 USB 2.0 Host/Function Module (USB)
When the selected pipe is for isochronous transfer, this module performs the following operations
while it controls the token issuance intervals. The module issues tokens even when the condition
for NRDY interrupt generation is met.
• When the selected pipe is for isochronous transfer and set in the IN direction:
The module issues an IN token and, if it does not receive packets from the function device
normally (i.e., no response or packet error), generates an NRDY interrupt.
If the time to issue an IN token comes in a situation where the module is unable to receive data
because of the full FIFO buffer, which may be caused by slow or delayed data reading from
the buffer or some other reasons, the module sets the OVRN bit to 1 and generates an NRDY
interrupt.
• When the selected pipe is for isochronous transfer and set in the OUT direction:
If the time to issue an OUT token comes in a situation where the FIFO buffer does not contain
any data ready for transmission because, for example, data writing to the FIFO buffer is slow
or delayed, the module sets the OVRN bit to 1, generates an NRDY interrupt, and transmits a
zero-length packet.
The interval of token issuance is reset by a power-on reset or when the ACLRM bit is set to 1.
(2) When the Function Controller Function is Selected
• When the selected pipe is for isochronous transfer and set in the OUT direction:
If the module does not receive any data packets within the (micro) frames for the interval
specified by the IITV bits, it generates an NRDY interrupt.
The module also generates an NRDY interrupt when it cannot receive a data packet normally
because any error, such as a CRC error, is found in the incoming data packet or when the
module is unable to receive data because of the full FIFO buffer, which may be caused by slow
or delayed data reading from the buffer or some other reasons.
An NRDY interrupt is generated with the timing of receiving an SOF packet. Even if the SOF
packet is corrupted, the interrupt is generated with the proper timing of SOF reception by the
internal interpolating function. Note that in the cases other than IITV = 0, an NRDY interrupt
is generated upon SOF packet reception at every interval after the counting of the interval is
started.
If the PID bits are set to NAK by software after the interval timer is started, this module does
not generate an NRDY interrupt even when it receives an SOF packet.
The conditions for starting the interval timer differ according to the IITV bit setting.
Rev. 1.00 Mar. 25, 2008 Page 1234 of 1868
REJ09B0372-0100