Queries on DMA

Few queries on DMA
1) What is a Burst size in DMA
2) What is the beat size for DMA
3) The DMA can have n beats/burst . What does it mean?
4) If i want to transfer 32 bytes of data and the burst size is 4
beats/burst then what should the beat size?
5) Do the source and destination bus width also effect the above
computation?


Thanks and Regards
Mohammed Anwar

P.S. If anyone can give me a link to web resource where i can find
some explanation on the above then it would be very helpful too

Silver
Thu Jul 12 13:43:10 CDT 2007

1,2,3)
burst, beat are not really anything to do with DMA, they are memory
controller settings.

A memory transaction looks like this:

<address> <data0> <data1> ... <dataN>

Burst Size is the number of bytes that can be transferred using a single
address cycle
Beats are the number of data cycles withing the burst.


4) If you have a 32 bit bus that uses 4 beat bursts then the burst size will
be 16 bytes.

If your bus is not 64 bits wide then you cannot transfer 32 bytes in a
single burst, you can only transfer 16 bytes.

5) yes, 1 beat transfer a data bus width's worth of data.

Geoff
--

PS your CPU documentation should provide a description of bursting.