Texas Instruments OMAP5912 Reference Manual page 1547

USB OTG Controller
set for non-USB functionality, the associated USB multiplexing port sees
6-/8-wire transceiver signaling, which implies that both D+ and D- are low. If
that pin group is associated with a host controller port, that host controller port
appears as a disconnected USB link. If that pin group is associated with the
device controller, the device controller sees USB reset signaling.
Functionality is undefined when top-level pin multiplexing selects non-USB
signalling of one or more of the pins that are required by the selected
HMC_MODE and transceiver signalling type. For example, if an HMC_MODE
value selects USB pin group 2 as a USB host connection and a 4-wire
transceiver interface is selected, but pin UART2.CTS/USB2.RCV top-level pin
multiplexing selects signal UART2.CTS, the associated USB host controller
port behavior is undefined.
Select USB and/or USB OTG Transceiver Type
USB connectivity on OMAP5912 USB pin group 1, USB pin group 2, and USB
alternate pin group 2 require external components, except for pin group 2
when it is configured for a TLL mode. Several different types of external
transceiver signaling are supported. Signaling between the OMAP5912 USB
controller and the external USB transceiver for monitoring and controlling the
differential USB signal can be via a 6-wire, 4-wire, or 3-wire signaling interface,
with two or more additional control signals provided either by additional signals
2
or via an I C link. OTG transceivers can support the 6-wire, 4-wire, and/or
2
3-wire basic signaling, but generally provide an interrupt output and an I C link
for the additional control and status reporting required by OTG functionality.
The figures referenced in the USB Pin Group 0, USB Pin Group 1, USB Pin
Group 2, and Alternate Pin Group 2 columns of Table 73 show external
connectivity options for each of the possible selections. Carefully examine the
options for the HMC_MODE you have identified.
Consider which OMAP5912 pins are required in each diagram and determine
if any particular choice (3-wire, 4-wire, or 6-wire) is advantageous in terms of
other non-USB functionality that is available for each pin group. Choose a
transceiver type.
A USB OTG transceiver can generally be used in place of a USB transceiver;
2
using an OTG transceiver with an I C interface can reduce the number of
OMAP5912 pins that are required. This can assist in making non-USB
functionality available on the USB pin groups.
SPRU761A Universal Serial Bus (USB) 255