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ice40: add support for both 1364.1 and LSE RAM/ROM attributes.

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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 appear to interpret attribute values insensitive
    to case. There is currently no way to do this in Yosys (attrmap
    can only change case of attribute names).
  * 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).
This commit is contained in:
whitequark 2020-01-01 06:18:53 +00:00
parent 29d130dee9
commit fc28bf55aa
4 changed files with 239 additions and 21 deletions
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42
tests/arch/common/blockram.v
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@ -5,19 +5,20 @@ module sync_ram_sp #(parameter DATA_WIDTH=8, ADDRESS_WIDTH=10)
input wire [ADDRESS_WIDTH-1:0] address_in,
output wire [DATA_WIDTH-1:0] data_out);
localparam WORD = (DATA_WIDTH-1);
localparam DEPTH = (2**ADDRESS_WIDTH-1);
localparam WORD = (DATA_WIDTH-1);
localparam DEPTH = (2**ADDRESS_WIDTH-1);
reg [WORD:0] data_out_r;
reg [WORD:0] memory [0:DEPTH];
reg [WORD:0] data_out_r;
reg [WORD:0] memory [0:DEPTH];
always @(posedge clk) begin
if (write_enable)
memory[address_in] <= data_in;
data_out_r <= memory[address_in];
end
always @(posedge clk) begin
if (write_enable)
memory[address_in] <= data_in;
data_out_r <= memory[address_in];
end
assign data_out = data_out_r;
assign data_out = data_out_r;
endmodule // sync_ram_sp
@ -28,18 +29,19 @@ module sync_ram_sdp #(parameter DATA_WIDTH=8, ADDRESS_WIDTH=10)
input wire [ADDRESS_WIDTH-1:0] address_in_r, address_in_w,
output wire [DATA_WIDTH-1:0] data_out);
localparam WORD = (DATA_WIDTH-1);
localparam DEPTH = (2**ADDRESS_WIDTH-1);
localparam WORD = (DATA_WIDTH-1);
localparam DEPTH = (2**ADDRESS_WIDTH-1);
reg [WORD:0] data_out_r;
reg [WORD:0] memory [0:DEPTH];
reg [WORD:0] data_out_r;
reg [WORD:0] memory [0:DEPTH];
always @(posedge clk) begin
if (write_enable)
memory[address_in_w] <= data_in;
data_out_r <= memory[address_in_r];
end
always @(posedge clk) begin
if (write_enable)
memory[address_in_w] <= data_in;
data_out_r <= memory[address_in_r];
end
assign data_out = data_out_r;
assign data_out = data_out_r;
endmodule // sync_ram_sdp