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https://github.com/YosysHQ/yosys
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081d9318bc
This commit tries to carefully follow the documented behavior of LSE
and Synplify. It will use `syn_ramstyle` attribute if there are any
write ports, and `syn_romstyle` attribute otherwise.
* LSE supports both `syn_ramstyle` and `syn_romstyle`.
* Synplify only supports `syn_ramstyle`, with same values as LSE.
* Synplify also supports `syn_rw_conflict_logic`, which is not
documented as supported for LSE.
Limitations of the Yosys implementation:
* LSE/Synplify support `syn_ramstyle="block_ram,no_rw_check"`
syntax to turn off insertion of transparency logic. There is
currently no way to support multiple valued attributes in
memory_bram. It is also not clear if that is a good idea, since
it can cause sim/synth mismatches.
* LSE/Synplify/1364.1 support block ROM inference from full case
statements. Yosys does not currently perform this transformation.
* LSE/Synplify propagate `syn_ramstyle`/`syn_romstyle` attributes
from the module to the inner memories. There is currently no way
to do this in Yosys (attrmvcp only works on cells and wires).
32 lines
911 B
Verilog
32 lines
911 B
Verilog
`default_nettype none
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module sync_rom #(parameter DATA_WIDTH=8, ADDRESS_WIDTH=10)
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(input wire clk,
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input wire [ADDRESS_WIDTH-1:0] address_in,
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output wire [DATA_WIDTH-1:0] data_out);
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localparam WORD = (DATA_WIDTH-1);
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localparam DEPTH = (2**ADDRESS_WIDTH-1);
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reg [WORD:0] data_out_r;
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reg [WORD:0] memory [0:DEPTH];
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integer i,j = 64'hF4B1CA8127865242;
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initial
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for (i = 0; i <= DEPTH; i++) begin
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// In case this ROM will be implemented in fabric: fill the memory with some data
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// uncorrelated with the address, or Yosys might see through the ruse and e.g. not
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// emit any LUTs at all for `memory[i] = i;`, just a latch.
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memory[i] = j * 64'h2545F4914F6CDD1D;
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j = j ^ (j >> 12);
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j = j ^ (j << 25);
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j = j ^ (j >> 27);
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end
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always @(posedge clk) begin
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data_out_r <= memory[address_in];
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end
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assign data_out = data_out_r;
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endmodule // sync_rom
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