Universal Serial Bus Interface – On-The-Go Module
MCF52277 Reference Manual, Rev. 1
20-46
Freescale Semiconductor
20.4.4.1
USB On-Chip Transceiver Required External Components
USB system operation does not require external components. However, the recommended method ensures
driver output impedance, eye diagram, and V
BUS
cable fault tolerance requirements are met. The
recommended method is for the DM and DP I/O pads to connect through series resistors (approximately
33
Ω
each) to the USB connector on the application printed circuit board (PCB). Additionally, signal
quality optimizes when these 33
Ω
resistors are mounted close to the processor rather than closer to the
USB board level connector.
NOTE
Internal pull-down resistors are included that keep the DP and DM ports in
a known quiescent state when the USB port is not used or when a USB cable
is not connected.
Also included is an internal 1.5k
Ω
pull-up resistor on DP controlled by the
Chapter 9, “Chip Configuration Module (CCM),”
for more
details.) This allows the OTG module to operate in full-speed device
operation. Host operation requires this internal resistor to be disabled via the
CCM, and 15k
Ω
external resistors to connect from DP and DM signals to
ground.
20.5
Initialization/Application Information
20.5.1
Host Operation
Enhanced Host Controller Interface (EHCI) Specification defines the general operational model for the
USB module in host mode. The EHCI specification describes the register-level interface for a host
controller for USB Revision 2.0. It includes a description of the hardware/software interface between
system software and host controller hardware. The next section has information about the initialization of
the USB modules; however, full details of the EHCI specification are beyond the scope of this document.
20.5.1.1
Host Controller Initialization
After initial power-on or module reset (via the USBCMD[RST] bit), all of the operational registers are at
default values, as illustrated in the register memory map in
.
Table 20-42. USB Network Speed and Required Physical Interface
USB Mode & Speed
DP & DN On-Chip
Analog XCVR
Active
I
2
C FEC
External Integrated Circuit Required
USB Host FS/LS
Yes
No
Yes See
Section 20.4.4.1, “USB On-Chip Transceiver
USB Device FS
Yes
No
Yes See
Summary of Contents for MCF52277
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Page 740: ...I2 C Interface MCF52277 Reference Manual Rev 1 31 16 Freescale Semiconductor...
Page 790: ...Debug Module MCF52277 Reference Manual Rev 1 32 50 Freescale Semiconductor...