Datasheet

 2017 Microchip Technology Inc. DS60001516A-page 689
SAM9G20
37. USB Host Port (UHP)
37.1 Overview
The USB Host Port (UHP) interfaces the USB with the host application. It handles Open HCI protocol (Open Host Controller Interface) as
well as USB v2.0 Full-speed and Low-speed protocols.
The USB Host Port integrates a root hub and transceivers on downstream ports. It provides several high-speed half-duplex serial com-
munication ports at a baud rate of 12 Mbit/s. Up to 127 USB devices (printer, camera, mouse, keyboard, disk, etc.) and the USB hub can
be connected to the USB host in the USB “tiered star” topology.
The USB Host Port controller is fully compliant with the Open HCI specification. The USB Host Port User Interface (registers description)
can be found in the Open HCI Rev 1.0 Specification available on www.hp.com. The standard OHCI USB stack driver can be easily ported
to Microchip’s architecture in the same way all existing class drivers run without hardware specialization.
This means that all standard class devices are automatically detected and available to the user application. As an example, integrating an
HID (Human Interface Device) class driver provides a plug & play feature for all USB keyboards and mouses.
37.2 Block Diagram
Figure 37-1: Block Diagram
Access to the USB host operational registers is achieved through the AHB bus slave interface. The Open HCI host controller initializes
master DMA transfers through the ASB bus master interface as follows:
• Fetches endpoint descriptors and transfer descriptors
• Access to endpoint data from system memory
• Access to the HC communication area
• Write status and retire transfer Descriptor
Memory access errors (abort, misalignment) lead to an “Unrecoverable Error” indicated by the corresponding flag in the host controller
operational registers.
The USB root hub is integrated in the USB host. Several USB downstream ports are available. The number of downstream ports can be
determined by the software driver reading the root hub’s operational registers. Device connection is automatically detected by the USB
host port logic.
USB physical transceivers are integrated in the product and driven by the root hub’s ports.
Over current protection on ports can be activated by the USB host controller. Microchip’s standard product does not dedicate pads to exter-
nal over current protection.
PORT S/M
PORT S/M
USB transceiver
USB transceiver
DP
DM
DP
DM
Embedded USB
v2.0 Full-speed Transceiver
Root Hub
and
Host SIE
List Processor
Block
FIFO 64 x 8
HCI
Slave Block
OHCI
Registers
OHCI Root
Hub Registers
AHB
ED & TD
Regsisters
Control
HCI
Master Block
Data
uhp_int
MCK
UHPCK
AHB
Slave
Master