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High-Speed USB Host Subsystem
The USBHOST_FLCK2 functional clock
is controlled by the PRCM register bit
PRCM.CM_FCLKEN_USBHOST[1]:
0: Disabled
1: Enabled
The CORE_120M_FCLK functional clock is used only by the USBTLL module (USBTLL_FCLK) in the
subsystem, and comes from the PRCM module.
This clock is controlled by the PRCM
register bit
PRCM.CM_FCLKEN3_CORE[2]:
0: Disabled
1: Enabled
22.2.3.1.3 Power-Management Scheme
22.2.3.1.3.1 High-Speed USB Host Controller Power-Management Scheme
22.2.3.1.3.1.1 Overview
To save dynamic power consumption, an efficient idle scheme in the device is based on the following:
•
An efficient local autoclock gating for each module
•
The implementation of control sideband signals between the PRCM module and each module
This enhanced idle control allows clocks to be activated/deactivated safely without complex software
intervention. In both cases, the high-speed USB host controller power management is applied only to the
interface clock domain.
The high-speed USB host controller has both master (initiator) and slave (target) interfaces.
•
As an initiator, the high-speed USB host controller implements the standby handshake protocol to
inform the PRCM module when it enters standby mode and does not generate traffic on the
interconnect.
•
As a target, the high-speed USB host controller implements the IDLE handshake protocol to allow the
PRCM module requiring it to enter idle mode.
details the high-speed USB host controller module PRCM clock control bits.
Table 22-37. High-Speed USB Host Controller PRCM Clock Control Bits
Module Clock
Associated PRCM Clock
Enabled Bit
Autoidle Bit
Output
USBHOST_FCLK1
USBHOST_48M_FCLK
PRCM.CM_FCLKEN_USBHOST[0]
N/A
EN_USBHOST1 bit
USBHOST_FCLK2
USBHOST_120M_FCLK
PRCM.CM_FCLKEN_USBHOST[1]
N/A
EN_USBHOST2 bit
USBHOST_MICLK
USBHOST_L3_ICLK
PRCM.CM_ICLKEN_USBHOST[0]
PRCM.CM_AUTOIDLE_USBHOST[0]
EN_USBHOST bit
AUTO_USBHOST bit
3265
SWPU177N – December 2009 – Revised November 2010
High-Speed USB Host Subsystem and High-Speed USB OTG Controller
Copyright © 2009–2010, Texas Instruments Incorporated
Содержание OMAP36 Series
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