ISP1362
Single-chip USB OTG controller
Philips Semiconductors
6. The A-device detects lack of bus activity for more than 3 ms and turns off its
DP pull-up. Alternatively, if the A-device has no further need to communicate with
the B-device, the A-device may turn off VBUS and end the session.
7. The B-device turns on its pull-up.
8. After waiting 30 µs to ensure that the DP line is not HIGH because of the residual
effect of the A-device pull-up, the A-device notices that the DP-line is HIGH (and
the DM line is LOW) indicating that the B-device is signaling a connect and is
ready to respond as a peripheral. At this point, the A-device becomes a host and
asserts the bus reset to start using the bus.
11.4.2 OTG state diagrams
Figure 18 and Figure 19 show the state diagrams for the dual-role A-device and the
dual-role B-device, respectively. For a detailed explanation, refer to On-The-Go
Supplement to the USB 2.0 Specification Rev. 1.0a.
The OTG state machine is implemented with software. The inputs to the state
machine come from four sources: hardware signals from the USB bus, software
signals from the application program, internal variables with the state machines and
timers:
• Hardware inputs: Include id, a_vbus_vld, a_sess_vld, b_sess_vld, b_sess_end,
a_conn, b_conn, a_bus_suspend, b_bus_suspend, a_bus_resume,
b_bus_resume, a_srp_det and b_se0_srp. All these inputs can be derived from
the OtgInterrupt and OtgStatus registers.
• Software inputs: Include a_bus_req, a_bus_drop and b_bus_req.
• Internal variables: Include a_set_b_hnp_en, b_hnp_enable and b_srp_done.
• Timers: The HNP state machine uses four timers: a_wait_vrise_tmr,
a_wait_bcon_tmr, a_aidl_bdis_tmr and b_ase0_brst, tmr. All timers are started on
entry to and reset on exit from their associated states. The ISP1362 provides a
programmable timer that can be used as any of these four timers.
9397 750 12337
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
Product data
Rev. 03 — 06 January 2004
35 of 150
NXP [ NXP ]
