SH7265 Datasheet, PDF (1403/2024 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7260 Series

Section 25 USB 2.0 Host/Function Module (USB)
25.4.9 SOF Interpolation Function
When the function controller function is selected and if data could not be received at intervals of 1
ms (when using full-speed operation) or 125 µs (when using high-speed operation) because an
SOF packet was corrupted or missing, this module interpolates the SOF. The SOF interpolation
operation begins when USBE = 1, SCKE = 1 and an SOF packet is received. The interpolation
function is initialized under the following conditions.
• Power-on reset
• USB bus reset
• Suspended state detected
Also, the SOF interpolation operates under the following specifications.
• 125 µs/1 ms conforms to the results of the reset handshake protocol.
• The interpolation function is not activated until an SOF packet is received.
• After the first SOF packet is received, either 125 µs or 1 ms is counted with an internal clock
of 48 MHz, and interpolation is carried out.
• After the second and subsequent SOF packets are received, interpolation is carried out at the
previous reception interval.
• Interpolation is not carried out in the suspended state or while a USB bus reset is being
received. (With suspended transitions in high-speed operation, interpolation continues for 3 ms
after the last packet is received.)
This module supports the following functions based on the SOF detection. These functions also
operate normally with SOF interpolation, if the SOF packet was corrupted.
• Refreshing of the frame number and the micro-frame number
• SOFR interrupt timing and µSOF lock
• Isochronous transfer interval count
If an SOF packet is missing when full-speed operation is being used, the FRNM bit in FRMNUM0
is not refreshed.
If a µSOF packet is missing during high-speed operation, the UFRNM bit in FRMNUM1 is
refreshed.
However, if a µSOF packet for which the µFRNM = 000 is missing, the FRNM bit is not
refreshed. In this case, the FRNM bit is not refreshed even if successive µSOF packets other than
µFRNM = 000 are received normally.
Rev. 1.00 Mar. 14, 2008 Page 1367 of 1984
REJ09B0351-0100