CHAPTER 6 USB CONTROLLER
330 Preliminary User’s Manual S15543EJ1V0UM

6.3 USB Attachment Sequence

This section describes the sequence that is followed when the
µ
PD98502 is attached to a USB hub.
Figure 6-2. USB Attachment Sequence
VR4120A USB
Controller
Connect to a HUB
Host PC resets
the Port that
the new device
is connected
(1)
Continues to issue
reset sign alling
for over 10 ms
The HUB detects that
a new device is
connected
Receives Reset
Signaling
It makes UR ST bit
in U_GSR2 register
active
Reads U_GSR2
register, detects
Reset Sig nalling
Host PC
Issues warm-reset
to USB Controller.
Stops Reset
Signaling
Sets initializa tion to
each register
(4)
(2)
(3)
(8)
(5)
(6)
(7)
(9)
µ
PD98502
(1) USB port of the
µ
PD98502 is attached to a HUB.
(2) Notification that a new device (
µ
PD98502) has been connected to the HUB is posted to a Host PC.
(3) The Host PC issues Reset Signaling to reset the port to which the device has been connected.
(4) Once 10 ms have elapsed, the Host PC halts the issue of the Reset Signaling.
(5) Notification of the Reset Signaling performed by the Host PC is posted to USB Controller.
(6) To post notification of the Reset by the Host PC to the VR4120A, the URST bit of the U_GSR2 register is made
active.
(7) The VR4120A reads the U_GSR2 register and, upon finding that the URST bit is active, detects that Reset
Signaling has been issued.
(8) To initialize USB Controller, the VR4120A has to issue the warm-reset to USB Controller.
(9) Upon the completion of the reset, USB Controller performs initialization by writing a value into each of USB
Controller's internal registers.