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DMA Controller PL230 - Representation of PL230_DMA_CHNL_BITS

hk_007

Hi, 

In DMA Controller(PL230) Technical Refrerence Manual r0p0, topic 3.2.3 Channel control data base pointer

It says that PL230_DMA_CHNL_BITS is defined as the minimum number of bits required to represent the number of DMA channels, minus one. But not followig this rule for number of channels > 1. 

Ex.

To represent 5 to 8 DMA channel, minimum number of bits required is 3. 3 - 1 = 2.

So PL230_DM_CHNL_BITS should be 2 as per rule but it is 3.

Can you help me to explain this ?

Parents
  • +1

    Hi All, 

    This is a simple grammatical issue, and the comma before minus one is what causes the confusion. The correct interpretation should be:

    PL230_DMA_CHNL_BITS = the minimum number of bits required to represent (number of DMA channels – 1).

    For example, if there are 5 to 8 DMA channels, then the values to represent are 4 to 7. The minimum number of bits required for this range is 3.

    Thanks & regards,

Reply
  • +1

    Hi All, 

    This is a simple grammatical issue, and the comma before minus one is what causes the confusion. The correct interpretation should be:

    PL230_DMA_CHNL_BITS = the minimum number of bits required to represent (number of DMA channels – 1).

    For example, if there are 5 to 8 DMA channels, then the values to represent are 4 to 7. The minimum number of bits required for this range is 3.

    Thanks & regards,

Children