M66596FP/WG
rev .1.00
2006.3.14
page 70 of 127
3.2.8
Frame refresh interrupt
Figure 3.18 shows an example of the SOFR interrupt output timing of the controller.
In the Host mode, the SOFR interrupt is generated when the frame number is refreshed,
In the Peripheral mode, the SOFR interrupt is generated, when the frame number is refreshed, or a damaged SOF
packet is detected. The interrupt operation should be specified using the SOFRM bit of the FRMNUM register.
(1) When “SOFRM=0” is selected
The SOFR interrupt is generated at the timing at which the frame number is refreshed (intervals of
approximately 1 ms). Interrupts are generated by the internal interpolation function even if an SOF packet is
damaged or missing. During Hi-Speed communication as well, interrupts are generated at the timing at which
the frame number is refreshed (intervals of approximately 1 ms).
(2) When “SOFRM=1” is selected
The SOFR interrupt is generated when SOF packets are damaged and when they are missing. During Hi-Speed
communication, the interrupt is generated only if the first packet of a uSOF packet with the same frame number
is damaged or missing.
(Corrupted and missing SOFs are recognized by the SOF interpolation function. For detailed information, please
refer to Chapter
0, SOF interpolation function.)
* SOFRM bit should not be set “SFRM=1” in the Host mode.
In the Peripheral mode, if the controller detects a new SOF packet during Full-Speed operation, it refreshes the
frame number and generates an SOFR interrupt. However, if the system does not enter the
SOF lock state during
Hi-Speed operation, the frame number is not refreshed, and no SOFR interrupt is generated. Also, the SOF
interpolation function is not activated. The
SOF lock state is the state in which uSOF packets with different frame
numbers are received twice in succession without an error occurring .
The conditions under which
SOF lock monitoring begins, and under which SOF lock monitoring stops, are as
noted below.
(1)
Conditions under which
SOF lock monitoring begins
USBE=1 and the internal clock (SCKE) is being supplied
(2)
Conditions under which
SOF lock monitoring stops
USBE=0 (S/W reset) or a USB bus reset is received, or a suspended state is detected
Peripheral Device
uSOF packet
uSOF number
Frame number
SOFR interrupt
(SOFRM=0)
(SOFRM=1)
uSOF Lock
uSOF packet
uSOF number
SOFR interrupt
uSOF lock
7
0
1
6
7
0
701
70
1
2
70
1
SOF interpolation, missing
Not locked
SOF interpolation
7
0
1
2
3
6
70
123
4
5
6
70
1
3
4
6
SOF interpolation function
SOF missing
SOF interpolation
45
Figure 3.18 Example of SOFR interrupt output timing