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2016-04-28 - Giant Gecko Family - d0053_Rev1.20
329
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Figure 15.34. HNP When the Core is an A-Device
Read
USB_GINTSTS
USB_GOTGINT.
HSTNEGDET
=1?
No
Yes
Read
USB_GINTSTS.CURMOD
Program USB_HPRT .PRTSUSP =
1
Unm ask USB_GINTSTS. OTGINT
Int errupt ?
Yes
No
Host t o Device t o Host
Program
USB_GOTGCTL .HSTSETHNPEN =
1
USB_GINTSTS.
OTGINT
=1 ?
No
Int errupt ?
Yes
No
Yes
USB_GINTSTS.
CURMOD = 0?
No
Rem ain as
Host
(The host ’ s
applicat ion can
t ake a call whet her
t o swit ch off VBUS
or not )
Yes
End of Device
t ransact ions
Read
USB_GINTSTS
1. Unm ask
USB_GINTSTS.ERLYSUSP
2. Device Init ializat ion St eps
.
For m ore inform at ion
Device Init ializat ion sect ion
of t his chapt er
.
St art of Device
t ransact ions
C1
C1
Int errupt ?
No
No
Yes
Read
USB_GINTSTS
Int errupt ?
No
No
Yes
A
-D
e
vi
ce
a
s
U
S
B
H
o
st
Read
USB_GINTSTS
Int errupt
wit hin
200 m s
yes
No
Yes
No
A
-D
e
vic
e
a
s
U
S
B
D
e
v
ic
e
Read USB_GINTSTS
Check t hat CURMOD
= 0
Host Mode
Transact ions
Yes
Applicat ion st art s
200
m s t im er
Host Init ializat ion
St eps .
For m ore
inform at ion
,
see Host
Init ializat ion sect ion
of t his chapt er
.
USB_GINTSTS.
ERLYSUSP = 1 ?
USB_GINTSTS.
USBSUSP = 1 ?
USB_GINTSTS.WKUPINT = 1
or
USB_GINTSTS.RESETDET ?
Host m ode
(Send Set Feat ure Com m and t o enable
b_hnp_enable feat ure in HNP capable
devices. HNP polling m echanism is also
involved. This is done when OTG FSM
is in a_host st at e)
, see
?
Figure 15.35 (p. 330) shows the programming steps that need to be performed by B-device’s
application (core as B-device) in order to change its role to Host. In Figure 15.35 (p. 330) , the B-
device performs a role change, becomes a Host and then reverts back to Device mode of operation.
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