Adding a Descriptor Between Existing Descriptors

To insert a new descriptor 'C' between two existing descriptors ('A' and 'B'), the descriptor currently executed by the DMA must be identified.

1. 1.If DMA is executing descriptor B, descriptor C cannot be inserted.
2. 2.If DMA has not started to execute descriptor A, follow the steps:
   1. a.Set the descriptor A VALID bit to '0'.
   2. b.Set the DESCADDR value of descriptor A to point to descriptor C instead of descriptor B.
   3. c.Set the DESCADDR value of descriptor C to point to descriptor B.
   4. d.Set the descriptor A VALID bit to '1'.
3. 3.If DMA is executing descriptor A:
   1. a.Apply the software suspend command to the channel and
   2. b.Perform steps 2.1 through 2.4.
   3. c.Apply the software resume command to the channel.