Is using a single 25MHz oscillator feasible

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originally posted by bkucera@Jul 4 2006, 12:05 AM

we're starting to design a custom board using a stratix ii part and we'd like the board to be as small as possible. the board will have an ethernet device, sram, cfi flash, and the max programming cpld from the dev board.

assuming we go with the lan91c111 for the ethernet device, would it be feasible to use a single 25mhz oscillator for the entire board? the max's design only runs at 3.125mhz so that shouldn't be an issue, and a pll can be used to make a custom target design so the flash programmer can run at 50mhz.

anyone else tried this, or know of a potential issue with using a single oscillator for the entire board?

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Hi!

I think you have not any problem for realize it!

1)You should use PLL for getting 50MHz from 25 MHz

2) 3.125 Mhz is equal 50Mhz divide by 16. It means simple counter with module 2