Focus Enhancements FS456 Data Sheet

is used to achieve the finest clock resolution, using a dithered clock.  In PLL mode, the NCO is bypassed 
and the clock is not dithered.  The NCO can be used when HTOTAL and VTOTAL values have additional 
constraints that prevent selection of values that are factors of the TV pixel rate. 

The FS453 registers are accessed through a serial input/output bus (SIO) which is I

2

SMBus-compatible.  These registers can be read or written at any time the part is receiving a reference 
clock at XTAL_IN and not being held in reset via the RESET_L pin. 

The Sync Timing Generator provides/accepts HSync, VSync, Field and Blank signals to/from the graphics 
controller.   

The FS453 can operate in pseudo-master mode or slave mode.  In pseudo-master mode, the GCC 
derives the VGA pixel clock, horizontal sync, and vertical sync from CLKOUT supplied by the FS453.  In 
slave mode, the GCC generates the pixel clock, syncs and data, and the FS453 must be programmed to 
generate the same pixel clock, using a common reference.  Use the slave mode when the GCC does not 
have a pixel clock input.   

 

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Note: I

2

C is a registered trademark of Philips Corporation.  The FS453 Serial I/O bus is similar but not identical to the Philips I

2

C 

bus.