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(7) USB SOF (Start of Frame) Interrupt
This interrupt is valid to control the isochronous transfer. When a valid SOF PID is detected, receive of
an SOF packet is recognized and an interrupt request occurs. The frame number (11 bits) of the SOF
packet received from the host is automatically stored in USB frame number register.
In isochronous transfer, P9
bit of USB control register. (Set P9
host, the P9
When using the USB SOF interrupt, set the interrupt priority level at USB SOF interrupt control register
(SOFIC: address 005B
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Artificial SOF Function
If the SOF packet from the host PC is destroyed due to any cause, and thus the SOF packet is not
correctly received within 1 ms of the start of the frame, a virtual SOF receive operation is performed
(and an USB SOF interrupt is generated). Even if the SOF packet is destroyed due to any cause, a
new frame can be formed by this function without waiting for the next SOF packet. This function
operates once to virtually receive an SOF packet after two SOF packets have been received cor-
rectly.
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
can be used as the SOF output pin by setting "1" to USB SOF port select
2
to output port.) Every time that the SOF signal is received from the
2
outputs "Low" for about 166ns (two cycles of the 12MHz USB clock.).
2
).
16
page 157 of 354
2. USB function
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