Themis USPIIi-1v, Hardware Manual

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USPIIi-1v Hardware Manual
5-16
Themis Computer
5.5.6 DMA Controller
The Universe IIB utilizes an internal DMA controller for high performance data transfer between the
VMEbus and the PCI bus. Universe IIB’s parameters for the DMA transfer are software configurable. DMA
operations between the source and destination bus are decoupled via the use of a single bidirectional FIFO
(DMAFIFO).
There are two modes of operation for the DMA: Linked List Mode and Direct Mode. In Linked List Mode,
the Universe IIB loads the DMA registers from PCI memory and executes the transfers described by these
registers. In the direct mode, the PCI master directly programs the DMA registers.
The DMA controller also utilizes the command packet. A command packet is a block of DMA registers stored
in PCI memory. A command packet may be linked to another command packet so that when the DMA has
finished the operations described by one command packet, the DMA controller can automatically move on to
the next command packet in the linked-list of command packets (refer to “DMA Controller” on page 2-77 of
the Universe II User’s Manual).