ISP1362EE/01 PHILIPS [NXP Semiconductors], ISP1362EE/01 Datasheet - Page 34

• Manufacturer Part Number: ISP1362EE/01
• Description: Single-chip Universal Serial Bus On-The-Go controller
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
9397 750 12337
Product data
11.4.1 Sequence of HNP events
11.4 Host Negotiation Protocol (HNP)
HNP is used to transfer control of the host role between the default host (A-device)
and the default peripheral (B-device) during a session. When the A-device is ready to
give up its role as a host, it will condition the B-device by SetFeature (b_hnp_enable)
and will go into ‘suspend’. If the B-device wants to use the bus at that time, it signals
a ‘disconnect’ to the A-device. Then, the A-device will take the role of a peripheral
and the B-device will take the role of a host.
The sequence of events for HNP as observed on the USB bus is illustrated in
Figure
As can be seen in
1. The A-device completes using the bus and stops all bus activity (that is,
2. The B-device detects that the bus is idle for more than 5 ms and begins HNP by
3. The A-device detects SE0 on the bus and recognizes this as a request from the
4. After waiting for 30 s to ensure that the DP line is not HIGH because of the
5. When the B-device completes using the bus, it stops all bus activity. Optionally,
Fig 17. HNP sequence of events.
DP Composite
suspends the bus).
turning off the pull-up on DP. This allows the bus to discharge to the SE0 state.
B-device to become a host. The A-device responds by turning on its DP pull-up
within 3 ms of first detecting SE0 on the bus.
residual effect of the B-device pull-up, the B-device notices that the DP line is
HIGH and the DM line is LOW (that is, J state). This indicates that the A-device
has recognized the HNP request from the B-device. At this point, the B-device
becomes a host and asserts bus reset to start using the bus. The B-device must
assert the bus reset (that is, SE0) within 1 ms of the time that the A-device turns
on its pull-up.
the B-device may turn on its DP pull-up at this time.
A-device
B-device
17.
Legend
Rev. 03 — 06 January 2004
Figure
DP driven
Pull-up dominates
Pull-down dominates
Normal bus activity
1
2
17:
3
4
Single-chip USB OTG controller
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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