NXP Semiconductors LPC24XX UM10237 - Manual (Page 417)

UM10237_4 © NXP B.V. 2009. All rights reserved.
User manual Rev. 04 — 26 August 2009 417 of 792
NXP Semiconductors
UM10237
Chapter 15: LPC24XX USB OTG controller
Note that only the subset of A-device HNP states and state transitions supported by
hardware are shown. Software is responsible for implementing all of the HNP states.
Figure 15–63 may appear to imply that the interrupt bits such as TMR should be polled,
but this is not necessary if the corresponding interrupt is enabled.
Following are code examples that show how the actions in Figure 15–63 are
accomplished. The examples assume that ISP1302 is being used as the external OTG
transceiver.
Fig 63. State transitions implemented in software during A-device switching from host to peripheral
HNP_SUCCESS set? HNP_FAILURE set? TMR set?
a_host
when host sends SET_FEATURE
with a_hnp_enable,
set A_HNP_TRACK
stop the OTG timer
a_suspend
a_host
a_wait_vfall
go to
a_peripheral
go to
go to
yes yes
yes
set BDIS_ACON_EN
in external OTG transceiver
load and enable OTG timer
clear BDIS_ACON_EN
bit in external OTG transceiver
clear BDIS_ACON_EN
bit in external OTG transceiver
discharge V BUS
stop OTG timer
suspend host on port 1
go to
no no
no