Freescale-semiconductor TWR-MCF52259-Ethenet Uživatelský manuál stáhnout pdf (Strana 129)

Introduction to USB

USB On-the-Go:

Negotiation process

Appendix A USB On-the-Go

1. OTG-A (host) enables OTG-B (device) to become host by sending

SetFeature (b_hnp_enable) command to OTG-B (device).

2. OTG-A (host) suspends bus signaling so that OTG-B (device) can

now become host.

3. OTG-B (device) detects Suspend condition and turns off pull-up

resistor.

4. Because HNP is enabled, OTG-A (host) interprets this

“disconnect” as a request by the OTG-B (device) to become host.

5. OTG-A (host) turns on its pull-up resistor and becomes

peripheral/device.

HNP (Host Negotiation Protocol):

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Freescale-semiconductor TWR-MCF52259-Ethenet Uživatelský manuál Strana 129