SH7764 Datasheet, PDF (1053/1752 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC Engine Family SH-4A Series

Section 21 USB 2.0 Host/Function Module (USB)
SOF
Normal transfer
Token corrupted
Packet inserted
Frame misaligned
Frame misaligned
Token delayed
Token
Token
Token
Token
Token
Token
Token
Token
Token
1
Token
1 Token
Token
1 Token
Token
Token
Token
Token
1 Token
1 Token
Token
Token
Token
1
1
Token
Figure 21.18 Example of an Interval Error Being Generated when IITV = 1
21.4.9 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 the USBE and SCKE bits in SYSCFG have been set to 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
Rev. 1.00 Nov. 22, 2007 Page 997 of 1692
REJ09B0360-0100