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Universal Serial Bus Interface – On-The-Go Module
Freescale Semiconductor
10-47
10.4
Functional Description
This module can be broken down into functional sub-blocks as described below.
10.4.1
System Interface
The system interface block contains all the control and status registers to allow a core to interface to the
module. These registers allow the processor to control the configuration and ascertain the capabilities of
the module and, they control the module’s operation.
10.4.2
DMA Engine
The USB module contains a local DMA engine. It is responsible for moving all of the data transferred over
the USB between the module and system memory. Like the system interface block, the DMA engine block
uses a simple synchronous bus signaling protocol.
The DMA controllers must access control information and packet data from system memory. Control
information is contained in link list based queue structures. The DMA controllers have state machines able
to parse data structures defined in the EHCI specification. In host mode, the data structures are EHCI
compliant and represent queues of transfers performed by the host controller, including the
split-transaction requests that allow an EHCI controller to direct packets to FS and LS speed devices. In
device mode, data structures are similar to those in the EHCI specification and used to allow device
responses to be queued for each of the active pipes in the device.
10.4.3
FIFO RAM Controller
The FIFO RAM controller is used for context information and to control FIFOs between the protocol
engine and the DMA controller. These FIFOs decouple the system processor/memory bus requests from
the extremely tight timing required by USB.
The use of the FIFO buffers differs between host and device mode operation. In host mode, a single data
channel maintains in each direction through the buffer memory. In device mode, multiple FIFO channels
maintain for each of the active endpoints in the system.
In host mode, the USB OTG modules use 16-byte transmit buffers and 16-byte receive buffers. For the
USB OTG module, device operation uses a single 16-byte receive buffer and a 16-byte transmit buffer for
each endpoint.
10.4.4
Physical Layer (PHY) Interface
Readers should familiarize themselves with chapter 7 of the
Universal Serial Bus Specification, Revision
2.0.
The USB OTG modules contain an on-chip digital to analog transceiver (XCVR) for DP and DN USB
network communication. The USB module defaults to FS XCVR operation and can communicate in LS.
The USB OTG module may interface to any ULPI compatible PHY as well.
Due to pin-count limitations the USB module only supports certain combinations of PHY interfaces and
USB functionality. Refer to the
for more information.
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...