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CHAPTER 6 USB CONTROLLER
Preliminary User’s Manual S14767EJ1V0UM00
441
The V
R
4120A RISC Processor is not permitted to write to other than USB Controller's USB General Mode Register
and USB Interrupt Mask Register2 while USB Controller is in the Suspend status. Otherwise, after USB Controller
enters the Resume status, its operation will be unpredictable.
6.7.2 Resume
The Resume sequence is shown below.
Figure 6-27. Resume Sequence
V
R
4120A
USB
Controller
Starts Resume
Signaling
(1)
20ms
More than 20ms
progress,stops
Resume Signaling
and for 2bit-time
executes EOP
Signaling
Makes URSM bit in
USB General
Status Register2
active, and
generates the
interruption to
V
R
4120A.
Receives USB
interruption, reads
status register.
Detects transit to
Resume state.
Host PC
Detects Resume
Signaling, transits
to Resume state.
Ends of Resume
processing
(2)
(3)
(4)
(5)
(6)
μ
PD98501
(1) The Host PC starts Resume Signaling. The Resume Signaling is passed to every device connected to the USB.
(2) After at least 20 ms have elapsed, the Host PC stops the Resume Signaling then performs EOP Signaling for a
2bit-time duration.
(3) This causes the Host PC to terminate its Resume processing.
(4) USB Controller receives the Resume Signaling.
(5) USB Controller makes the URSM bit (Bit18) of the USB General Status Register2 (Address: 18H) active, then
issues an interrupt to the V
R
4120A RISC Processor. If clock supplement is stopped, V
R
4120A RISC Processor
has to check “usbwakeup_p” signal instead of “URSM” bit.
(6) The V
R
4120A RISC Processor receives the interrupt from USB Controller and, as a result, determines that the
USB has entered the Resume status.
After USB Controller enters the Resume status, it continues with the send/receive processing it was performing
immediately before it entered the Suspend status.