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mcf54415 ddr2 clock speed

Question asked by Angelo Dureghello on May 11, 2017
Latest reply on May 29, 2017 by Angelo Dureghello

Hi all,

have a queston on ddr2 clock speed on mcf54415 custom board.

 

What i actually so is :

- pll setup, i have

  fref = 30Mhz,

  refdiv = 0 (refdiv_divider = 1),

  cpu_clock configured to 240Mhz

  vco clock fixed at cpu_clock * 2,

  bus_clock at cpu_clock / 2

 

- ddr2 (128MB) init / setup

- memtest, passes all 128MB

 

- finally, DDR2 clock checked by scope, i see a syn at abt 240Mhz.

 

Strangely, since i set that that ddr2 clock must come from VCO, with

 

    /* use vco instead of cpu 2x clock for ddr clock */
    move.l    #MISCCR2, %a1
    move.w    #0xe01d, (%a1)
    /* use cpu clock */
    /* move.w    #0xa01d, (%a1) */

 

should i expect 480Mhz as ddr2 clock and 240 only if i set ddr2 clock coming from cpu clock ?

 

Thanks

angelo

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