USB Host Controller Overview
7-185
MPU Public Peripherals
7.14 USB Host Controller Overview
The OMAP5910 device implements a three-port USB host controller that is
compatible with the USB Revision 1.1 specification and the Open Host
Controller Interface Specification for USB (OHCI) Revision 1.0a. It provides
USB host connectivity for USB low-speed (1.5M bit/sec maximum) and full-
speed (12M bit/sec maximum) devices.
For details, see Chapter 14, Universal Serial Bus Host.
7.15 HDQ and 1-Wire Protocols
This module implements the hardware protocol of the master function of the
HDQ
and the 1-Wire
protocol.
This module works off a command structure that is programmed into transmit
command registers. The received data is in the receive data register. The
firmware is responsible for performing correct sequencing in the command
registers. The module only implements the hardware interface layer of the
protocols.
The HDQ and the 1-Wire modes are selectable in software, and this must be
done before any transmit and receive from the module is performed. The mode
is assumed static during operation of the device. From a timing perspective,
both the 1-Wire and the HDQ protocols use HDQ timing.
7.15.1 Functional Description
The module is intended to work with both the HDQ and the 1-Wire protocols.
The protocols use a single wire to communicate between the master and the
slave. The protocols employ a return-to-1 mechanism, where after any
command the line is pulled up to a high. This necessitates an external pullup.
An open-drain configuration is used on the wire. Therefore, the HDQ pin only
actively drives low and goes to the high-impedance state otherwise, allowing
an external pullup resistor to pull the wire high.
A control bit selects whether the HDQ or the 1-Wire protocol is to be used. This
bit should not be modified during active data cycles on the interface. There-
fore, it is recommended that the bit be only modified as part of boot up configu-
ration. For the design, the bit is assumed static. By default, the configuration
complies with the HDQ spec.
USB Host Controller Overview / HDQ and 1-Wire Protocol