What is the catch with IDMA on MPC860?

Noah Misch nmisch at erols.com
Thu Mar 23 09:59:15 EST 2000

Would you mind telling me briefly what CPM, UART, DMA/IDMA, UPM, and SCC
are, or pointing me to a document that explains them?  I see these terms
used a lot, but I don't know what they stand for and have only a general
idea of what they are.  I apologize for wasting your time with a worthless


>Just be sure you don't overtax your CPM.  20/27.45 = 73%,
>but if you start adding in UARTs, etc, you might be getting
>close to the edge.


>> I can live with the fact that IDMA can not utilize the
>> bus 100% of the time as long as it __relinquish the bus__
>> at all times it does not perform __full speed__ data
>> movements. Actually I prefer it does just that.


>> > Er, you're doing DMA to/from a memory.  The timing of that
>> > memory controls /TA.  If you're using your DRAM with one
>> > of the UPMs, and you're targeting that DRAM with IDMA, it
>> > uses the UPM to control the DRAM. (For a flyby-mode transaction).

Noah Misch
nmisch at erols.com

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