96
RSP Coprocessor 0
DMA
All data operated on by the RSP must first be DMA’d into DMEM. RSP
programs can also use DMA to load microcode into IMEM.
Note:
loading microcode on top of the currently executing code at the PC
will result in undefined behavior.
Alignment Restrictions
All data sources and destinations for DMA transfers must be aligned to
8 bytes (64 bits), in both DRAM and I/DMEM.
Transfer lengths must be multiples of 8 bytes (64 bits).
Timing
Peak transfer rate is 8 bytes (64 bits) per cycle. There is a DMA setup
overhead of 6-12 clocks, so longer transfers are more efficient.
IMEM and DMEM are single-ported memories, so accesses during DMA
transfers will impact performance.
DMA Full
The DMA registers are double-buffered, having one pending request and
one current active request. The
DMA FULL
condition means that there is an
active request and a pending request, so no more requests can be serviced.
DMA Wait
Waiting for DMA completion is under complete programmer control. When
DMA_BUSY
is cleared, the transaction is complete.
If there is a pending DMA transaction, this transaction will be serviced
before
DMA_BUSY
is cleared.
Summary of Contents for Ultra64
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