ISP1761BE STEricsson, ISP1761BE Datasheet - Page 88

• Manufacturer Part Number: ISP1761BE
• Manufacturer: STEricsson

Specifications of ISP1761BE

• Operating Temperature (min): -40C
• Operating Temperature Classification: Industrial
• Operating Temperature (max): 85C
• Package Type: LQFP
• Rad Hardened: No
• Lead Free Status / Rohs Status: Supplier Unconfirmed

NXP Semiconductors
ISP1761_5
Product data sheet
9.4.1 Sequence of HNP events
9.4 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 using 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
As can be seen in
1. The A-device completes using the bus and stops all bus activity, that is, suspends the
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 residual
5. When the B-device completes using the bus, it stops all bus activities. Optionally, the
Fig 14. HNP sequence of events
DP Composite
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.
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.
B-device may turn on its DP pull-up at this time.
Remark: The bus idle state will generate a DC suspend interrupt corresponding to the
toggle of the SUSP bit in the DcInterrupt register (address: 218h), when accordingly
enabled.
A-device
B-device
Legend
Figure
Rev. 05 — 13 March 2008
DP driven
Pull-up dominates
Pull-down dominates
Normal bus activity
1
14:
2
3
4
Hi-Speed USB OTG controller
5
6
7
© NXP B.V. 2008. All rights reserved.
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