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CSI State
The programmer-visible registers of CSI
are referred collectively to as the
CSI register space.
The CSI register space is depicted in Figure 6 and
consists of the stream control registers (SCRs), the
mask stream control registers (MSCRs),
the stream status register (SSR), the integer packed accumulator
register (pacc_int), and the floating-point packed accumulator
register (pacc_fp).
Figure 6:
The CSI register space.
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There are 96 32-bit stream control registers (SCRs) organized
in 16 sets, 8 registers per set.
Each set of the stream control registers, or SCR-set,
contains the parameters that completely specify a CSI arithmetic stream,
and, additionally, some parameters that specify the position of the current element
when the stream is processed by a CSI instruction.
The 48 32-bit mask stream control registers (MSCRs) are organized
in 16 MSCR-sets, 3 registers per set, and are used to specify bitstreams.
For a more detailed description of control registers and their function refer to
the
PACT-01 paper and the
PDCS-02 paper
The SSR register is used for control purposes, and the accumulation registers
are used to facilitate parallel accumulations.
Sizes of accumulation registers are implementation-dependent and determined by the
parameter SIMD_width, which designates the width of the datapath of the CSI execution unit in bytes.
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