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Using the external oscillator
50
NS7520 Hardware Reference, Rev. D 03/2006
NS7520 clock module block diagram
This diagram provides an overview of the clock module.
Using the external oscillator
The NS7520 can use an external oscillator to generate the BCLK and FXTAL signals. In
this type of configuration, the BCLK frequency is equal to the oscillator input
frequency. The FXTAL frequency is equal to the oscillator input frequency divided by
five. For example, with a 55MHz oscillator, BCLK would be 55 MHZ and FXTAL would
be 11MHz.
100PLL, boundary scan
101N/A
110PLL, JTAG debugger
111External oscillator, JTAG debugger
PLLTST BISTEN SCANEN FUNCTION
PLL
circuit
SCANEN PLLTST BISTEN
External
crystal
External
oscillator
A[8:0]
PLL Settings reg
PLL Control reg
/5
FXTAL
BCLK