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Section 26 USB 2.0 Host/Function Module
R01UH0134EJ0400 Rev. 4.00 Page 1543 of 2108
Sep 24, 2014
SH7262 Group, SH7264 Group
Token Token Token Token
Token Token Token
Token Token Token Token
Token Token Token
Token Token Token Token
Token Token Token
Token
Token
1
1
1
1 1
1 1
SOF
Token
Token
Token received at the frame other than the specified interval
(1) Normal transfer
(2) Token corrupted
(3) Packet inserted
(4) Frame misaligned 1
(5) Frame misaligned 2
(6) Token delayed
Interval when IITV = 1
Token received at the specified interval
Figure 26.22 Example of an Interval Error Being Generated when IITV = 1
26.4.9 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 s (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 s/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 s 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.