Paul Hodgskin

Using DDR2 memory with coldfire 54450 processor

Discussion created by Paul Hodgskin on Jul 15, 2008
Latest reply on Aug 1, 2008 by ricardo ricardo
I would like to use DDR2 memory with the MCF54450 processor which has an in built DDR memory controller.  The 5445x datasheet specifies that the 54450 and 51 devices can only run up to a maximum of 240MHz, giving a bus clock maximum of 120MHz.

DDR2 memory requires a bus clock maximum period of 8nS, meaning the bus frequency needs to be 125MHz.

Can someone please confirm that these figures are correct and if so, what effect does it have on the memory if it is slightly underclocked ?

If underclocking the memory is a problem, does anyone have any ideas whether slightly overclocking the coldfire to 250MHz to get the correct bus clock is a bad idea ?

Thank you in advance,

Paul H