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50 lines
1.4 KiB
ReStructuredText
50 lines
1.4 KiB
ReStructuredText
Coarse arithmetics
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------------------
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.. todo:: Add information about `$alu`, `$fa`, `$macc_v2`, and `$lcu` cells.
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The `$macc` cell type represents a generalized multiply and accumulate
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operation. The cell is purely combinational. It outputs the result of summing up
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a sequence of products and other injected summands.
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.. code-block::
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Y = 0 +- a0factor1 * a0factor2 +- a1factor1 * a1factor2 +- ...
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+ B[0] + B[1] + ...
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The A port consists of concatenated pairs of multiplier inputs ("factors"). A
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zero length factor2 acts as a constant 1, turning factor1 into a simple summand.
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In this pseudocode, ``u(foo)`` means an unsigned int that's foo bits long.
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.. code-block::
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struct A {
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u(CONFIG.mul_info[0].factor1_len) a0factor1;
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u(CONFIG.mul_info[0].factor2_len) a0factor2;
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u(CONFIG.mul_info[1].factor1_len) a1factor1;
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u(CONFIG.mul_info[1].factor2_len) a1factor2;
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...
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};
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The cell's ``CONFIG`` parameter determines the layout of cell port ``A``. The
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CONFIG parameter carries the following information:
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.. code-block::
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struct CONFIG {
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u4 num_bits;
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struct mul_info {
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bool is_signed;
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bool is_subtract;
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u(num_bits) factor1_len;
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u(num_bits) factor2_len;
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}[num_ports];
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};
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B is an array of concatenated 1-bit-wide unsigned integers to also be summed up.
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.. autocellgroup:: arith
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:members:
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:source:
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:linenos:
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