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5.2.1 Video Processing Back End Clocking
5.2.2 USB Clocking
Peripheral Clocking Considerations
The Video Processing Back End (VPBE) is a sub-module of the VPSS (Video Processing Subsystem).
The VPBE is designed to interface with a variety of LCDs and an internal DAC module. There are two
asynchronous clock domains in the VPBE: an internal clock domain and an external clock domain. The
internal clock domain is dvien by the VPSS clock (PLL1 SYSCLK4). The external clock domain is
configurable; you can select one of five source:
•
24 MHz crystal input at MXI1
•
27 MHz crystal input at MXI2 (optional feature)
•
PLL1 SYSCLK3
•
EXTCLK pin (external VPBE clock input pin)
•
PCLK pin (VPFE pixel clock input pin)
See the TMS320DM355 DMSoC Video Processing Back End (VPBE) Reference Guide for complete
information on VPBE clocking.
The USB Controller is driven by two clocks: an output clock of PLL1 and an output clock of the USB Phy.
The USB Phy clock is configurable by the USB Phy clock source bits (PHYCLKSRC) in the USB Phy
control register (USB_PHY_CTL) in the System Control Module. USBPHY_CTL is described in
When a 24-MHz crystal is used at MXI1/MXO1, set PHYCLKSRC to 0. This will present a 24-MHz clock to
the USB Phy. When a 36-MHz crystal is used at MXI1/MXO1, set PHYCLKSRC to 1. This will present a
12-MHz (36 MHz divided by three) crystal to the USB Phy. The USB Phy is capable of accepting only 24
MHz and 12 MHz; thus for USB support you must use either a 24-MHz or 36-MHz crystal at MXI1/MXO1.
See the TMS320DM355 DMSoC Univeral Serial Bus (USB) Controller Reference Guide (SPRUED2) for
more information.
SPRUFB3 – September 2007
Device Clocking
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