Merge pull request #728 from YosysHQ/gatecat/nexus-ram

interchange/nexus: Add RAM techmap rule and a RAM test

7 files changed, 384 insertions, 2 deletions

diff --git a/.github/workflows/interchange_ci.yml b/.github/workflows/interchange_ci.yml
index ee42d09e..d7dca9da 100644
--- a/.github/workflows/interchange_ci.yml
+++ b/.github/workflows/interchange_ci.yml
@@ -114,8 +114,8 @@ jobs:
       env:
         RAPIDWRIGHT_PATH: ${{ github.workspace }}/RapidWright
         PYTHON_INTERCHANGE_PATH: ${{ github.workspace }}/python-fpga-interchange
-        PYTHON_INTERCHANGE_TAG: v0.0.14
-        PRJOXIDE_REVISION: 82b23868d768dac9a5541331e3ddc4c4062627f7
+        PYTHON_INTERCHANGE_TAG: v0.0.15
+        PRJOXIDE_REVISION: 1bf30dee9c023c4c66cfc44fd0bc28addd229c89
         DEVICE: ${{ matrix.device }}
       run: |
         export PATH="/usr/lib/ccache:/usr/local/opt/ccache/libexec:$PATH"
diff --git a/fpga_interchange/examples/remap_nexus.v b/fpga_interchange/examples/remap_nexus.v
index fa817762..861ce779 100644
--- a/fpga_interchange/examples/remap_nexus.v
+++ b/fpga_interchange/examples/remap_nexus.v
@@ -2,3 +2,179 @@
 module INV(input A, output Z);
 	LUT4 #(.INIT("0x5555")) _TECHMAP_REPLACE_ (.A(A), .B(1'b1), .C(1'b1), .D(1'b1), .Z(Z));
 endmodule
+
+module PDPSC16K (...);
+	parameter DATA_WIDTH_W = "X36";
+	parameter DATA_WIDTH_R = "X36";
+	parameter OUTREG = "BYPASSED";
+	parameter RESETMODE = "SYNC";
+	parameter GSR = "ENABLED";
+	parameter ECC = "DISABLED";
+	parameter INITVAL_00 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_01 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_02 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_03 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_04 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_05 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_06 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_07 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_08 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_09 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_0A = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_0B = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_0C = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_0D = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_0E = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_0F = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_10 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_11 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_12 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_13 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_14 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_15 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_16 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_17 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_18 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_19 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_1A = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_1B = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_1C = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_1D = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_1E = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_1F = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_20 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_21 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_22 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_23 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_24 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_25 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_26 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_27 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_28 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_29 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_2A = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_2B = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_2C = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_2D = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_2E = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_2F = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_30 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_31 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_32 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_33 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_34 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_35 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_36 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_37 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_38 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_39 = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_3A = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_3B = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_3C = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_3D = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_3E = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter INITVAL_3F = "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000";
+	parameter CSDECODE_W = "000";
+	parameter CSDECODE_R = "000";
+	parameter ASYNC_RST_RELEASE = "SYNC";
+	parameter INIT_DATA = "STATIC";
+	input [35:0] DI;
+	input [13:0] ADW;
+	input [13:0] ADR;
+	input CLK;
+	input CER;
+	input CEW;
+	input [2:0] CSW;
+	input [2:0] CSR;
+	input RST;
+	output [35:0] DO;
+	output ONEBITERR;
+	output TWOBITERR;
+
+	// TODO: this should really be a macro or otherwise dealt with more automatically
+	PDPSC16K_MODE #(
+		.DATA_WIDTH_W(DATA_WIDTH_W),
+		.DATA_WIDTH_R(DATA_WIDTH_R),
+		.OUTREG(OUTREG),
+		.GSR(GSR),
+		.ECC(ECC),
+		.CSDECODE_W(CSDECODE_W),
+		.CSDECODE_R(CSDECODE_R),
+		.ASYNC_RST_RELEASE(ASYNC_RST_RELEASE),
+		.INITVAL_00(INITVAL_00),
+		.INITVAL_01(INITVAL_01),
+		.INITVAL_02(INITVAL_02),
+		.INITVAL_03(INITVAL_03),
+		.INITVAL_04(INITVAL_04),
+		.INITVAL_05(INITVAL_05),
+		.INITVAL_06(INITVAL_06),
+		.INITVAL_07(INITVAL_07),
+		.INITVAL_08(INITVAL_08),
+		.INITVAL_09(INITVAL_09),
+		.INITVAL_0A(INITVAL_0A),
+		.INITVAL_0B(INITVAL_0B),
+		.INITVAL_0C(INITVAL_0C),
+		.INITVAL_0D(INITVAL_0D),
+		.INITVAL_0E(INITVAL_0E),
+		.INITVAL_0F(INITVAL_0F),
+		.INITVAL_10(INITVAL_10),
+		.INITVAL_11(INITVAL_11),
+		.INITVAL_12(INITVAL_12),
+		.INITVAL_13(INITVAL_13),
+		.INITVAL_14(INITVAL_14),
+		.INITVAL_15(INITVAL_15),
+		.INITVAL_16(INITVAL_16),
+		.INITVAL_17(INITVAL_17),
+		.INITVAL_18(INITVAL_18),
+		.INITVAL_19(INITVAL_19),
+		.INITVAL_1A(INITVAL_1A),
+		.INITVAL_1B(INITVAL_1B),
+		.INITVAL_1C(INITVAL_1C),
+		.INITVAL_1D(INITVAL_1D),
+		.INITVAL_1E(INITVAL_1E),
+		.INITVAL_1F(INITVAL_1F),
+		.INITVAL_20(INITVAL_20),
+		.INITVAL_21(INITVAL_21),
+		.INITVAL_22(INITVAL_22),
+		.INITVAL_23(INITVAL_23),
+		.INITVAL_24(INITVAL_24),
+		.INITVAL_25(INITVAL_25),
+		.INITVAL_26(INITVAL_26),
+		.INITVAL_27(INITVAL_27),
+		.INITVAL_28(INITVAL_28),
+		.INITVAL_29(INITVAL_29),
+		.INITVAL_2A(INITVAL_2A),
+		.INITVAL_2B(INITVAL_2B),
+		.INITVAL_2C(INITVAL_2C),
+		.INITVAL_2D(INITVAL_2D),
+		.INITVAL_2E(INITVAL_2E),
+		.INITVAL_2F(INITVAL_2F),
+		.INITVAL_30(INITVAL_30),
+		.INITVAL_31(INITVAL_31),
+		.INITVAL_32(INITVAL_32),
+		.INITVAL_33(INITVAL_33),
+		.INITVAL_34(INITVAL_34),
+		.INITVAL_35(INITVAL_35),
+		.INITVAL_36(INITVAL_36),
+		.INITVAL_37(INITVAL_37),
+		.INITVAL_38(INITVAL_38),
+		.INITVAL_39(INITVAL_39),
+		.INITVAL_3A(INITVAL_3A),
+		.INITVAL_3B(INITVAL_3B),
+		.INITVAL_3C(INITVAL_3C),
+		.INITVAL_3D(INITVAL_3D),
+		.INITVAL_3E(INITVAL_3E),
+		.INITVAL_3F(INITVAL_3F),
+		.INIT_DATA(INIT_DATA)
+	) _TECHMAP_REPLACE_ (
+		.CLK(CLK), .CER(CER), .CEW(CEW), .RST(RST),
+		.CSW0(CSW[0]), .CSW1(CSW[1]), .CSW2(CSW[2]),
+		.CSR0(CSR[0]), .CSR1(CSR[1]), .CSR2(CSR[2]),
+		.DI0(DI[0]), .DI1(DI[1]), .DI2(DI[2]), .DI3(DI[3]), .DI4(DI[4]), .DI5(DI[5]), .DI6(DI[6]), .DI7(DI[7]), .DI8(DI[8]), .DI9(DI[9]), .DI10(DI[10]), .DI11(DI[11]), .DI12(DI[12]), .DI13(DI[13]), .DI14(DI[14]), .DI15(DI[15]), .DI16(DI[16]), .DI17(DI[17]), .DI18(DI[18]), .DI19(DI[19]), .DI20(DI[20]), .DI21(DI[21]), .DI22(DI[22]), .DI23(DI[23]), .DI24(DI[24]), .DI25(DI[25]), .DI26(DI[26]), .DI27(DI[27]), .DI28(DI[28]), .DI29(DI[29]), .DI30(DI[30]), .DI31(DI[31]), .DI32(DI[32]), .DI33(DI[33]), .DI34(DI[34]), .DI35(DI[35]),
+		.ADW0(ADW[0]), .ADW1(ADW[1]), .ADW2(ADW[2]), .ADW3(ADW[3]), .ADW4(ADW[4]), .ADW5(ADW[5]), .ADW6(ADW[6]), .ADW7(ADW[7]), .ADW8(ADW[8]), .ADW9(ADW[9]), .ADW10(ADW[10]), .ADW11(ADW[11]), .ADW12(ADW[12]), .ADW13(ADW[13]),
+		.ADR0(ADR[0]), .ADR1(ADR[1]), .ADR2(ADR[2]), .ADR3(ADR[3]), .ADR4(ADR[4]), .ADR5(ADR[5]), .ADR6(ADR[6]), .ADR7(ADR[7]), .ADR8(ADR[8]), .ADR9(ADR[9]), .ADR10(ADR[10]), .ADR11(ADR[11]), .ADR12(ADR[12]), .ADR13(ADR[13]),
+		.DO0(DO[0]), .DO1(DO[1]), .DO2(DO[2]), .DO3(DO[3]), .DO4(DO[4]), .DO5(DO[5]), .DO6(DO[6]), .DO7(DO[7]), .DO8(DO[8]), .DO9(DO[9]), .DO10(DO[10]), .DO11(DO[11]), .DO12(DO[12]), .DO13(DO[13]), .DO14(DO[14]), .DO15(DO[15]), .DO16(DO[16]), .DO17(DO[17]), .DO18(DO[18]), .DO19(DO[19]), .DO20(DO[20]), .DO21(DO[21]), .DO22(DO[22]), .DO23(DO[23]), .DO24(DO[24]), .DO25(DO[25]), .DO26(DO[26]), .DO27(DO[27]), .DO28(DO[28]), .DO29(DO[29]), .DO30(DO[30]), .DO31(DO[31]), .DO32(DO[32]), .DO33(DO[33]), .DO34(DO[34]), .DO35(DO[35]),
+		.ONEBITERR(ONEBITERR), .TWOBITERR(TWOBITERR),
+	);
+
+endmodule
diff --git a/fpga_interchange/examples/tests/CMakeLists.txt b/fpga_interchange/examples/tests/CMakeLists.txt
index 29106f12..1d3dd72f 100644
--- a/fpga_interchange/examples/tests/CMakeLists.txt
+++ b/fpga_interchange/examples/tests/CMakeLists.txt
@@ -6,3 +6,4 @@ add_subdirectory(ff)
 add_subdirectory(lut)
 add_subdirectory(lut_nexus)
 add_subdirectory(lutram)
+add_subdirectory(ram_nexus)
diff --git a/fpga_interchange/examples/tests/ram_nexus/CMakeLists.txt b/fpga_interchange/examples/tests/ram_nexus/CMakeLists.txt
new file mode 100644
index 00000000..49d976c5
--- /dev/null
+++ b/fpga_interchange/examples/tests/ram_nexus/CMakeLists.txt
@@ -0,0 +1,10 @@
+add_interchange_group_test(
+    name ram_nexus
+    family ${family}
+    board_list lifcl40evn
+    tcl run_nexus.tcl
+    sources ram_nexus.v
+    techmap ../../remap_nexus.v
+    skip_dcp
+)
+
diff --git a/fpga_interchange/examples/tests/ram_nexus/lifcl40evn.xdc b/fpga_interchange/examples/tests/ram_nexus/lifcl40evn.xdc
new file mode 100644
index 00000000..2fb0b3a2
--- /dev/null
+++ b/fpga_interchange/examples/tests/ram_nexus/lifcl40evn.xdc
@@ -0,0 +1,57 @@
+set_property PACKAGE_PIN L13 [get_ports clk]
+
+set_property PACKAGE_PIN E17 [get_ports led[0]]
+set_property PACKAGE_PIN F13 [get_ports led[1]]
+set_property PACKAGE_PIN G13 [get_ports led[2]]
+set_property PACKAGE_PIN F14 [get_ports led[3]]
+set_property PACKAGE_PIN L16 [get_ports led[4]]
+set_property PACKAGE_PIN L15 [get_ports led[5]]
+set_property PACKAGE_PIN L20 [get_ports led[6]]
+set_property PACKAGE_PIN L19 [get_ports led[7]]
+set_property PACKAGE_PIN R17 [get_ports led[8]]
+set_property PACKAGE_PIN R18 [get_ports led[9]]
+set_property PACKAGE_PIN U20 [get_ports led[10]]
+set_property PACKAGE_PIN T20 [get_ports led[11]]
+set_property PACKAGE_PIN W20 [get_ports led[12]]
+set_property PACKAGE_PIN V20 [get_ports led[13]]
+
+set_property PACKAGE_PIN G14 [get_ports pb0]
+set_property PACKAGE_PIN G15 [get_ports pb1]
+
+set_property PACKAGE_PIN N14 [get_ports sw[0]]
+set_property PACKAGE_PIN M14 [get_ports sw[1]]
+set_property PACKAGE_PIN M16 [get_ports sw[2]]
+set_property PACKAGE_PIN M15 [get_ports sw[3]]
+set_property PACKAGE_PIN N15 [get_ports sw[4]]
+set_property PACKAGE_PIN N16 [get_ports sw[5]]
+set_property PACKAGE_PIN M17 [get_ports sw[6]]
+set_property PACKAGE_PIN M18 [get_ports sw[7]]
+
+set_property IOSTANDARD LVCMOS33 [get_ports clk]
+
+set_property IOSTANDARD LVCMOS33 [get_ports led[0]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[1]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[2]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[3]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[4]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[5]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[6]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[7]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[8]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[9]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[10]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[11]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[12]]
+set_property IOSTANDARD LVCMOS33 [get_ports led[13]]
+
+set_property IOSTANDARD LVCMOS33 [get_ports pb0]
+set_property IOSTANDARD LVCMOS33 [get_ports pb1]
+
+set_property IOSTANDARD LVCMOS33 [get_ports sw[0]]
+set_property IOSTANDARD LVCMOS33 [get_ports sw[1]]
+set_property IOSTANDARD LVCMOS33 [get_ports sw[2]]
+set_property IOSTANDARD LVCMOS33 [get_ports sw[3]]
+set_property IOSTANDARD LVCMOS33 [get_ports sw[4]]
+set_property IOSTANDARD LVCMOS33 [get_ports sw[5]]
+set_property IOSTANDARD LVCMOS33 [get_ports sw[6]]
+set_property IOSTANDARD LVCMOS33 [get_ports sw[7]]
\ No newline at end of file
diff --git a/fpga_interchange/examples/tests/ram_nexus/ram_nexus.v b/fpga_interchange/examples/tests/ram_nexus/ram_nexus.v
new file mode 100644
index 00000000..e91a64bc
--- /dev/null
+++ b/fpga_interchange/examples/tests/ram_nexus/ram_nexus.v
@@ -0,0 +1,123 @@
+module ram0(
+    // Write port
+    input wrclk,
+    input [7:0] di,
+    input wren,
+    input [5:0] wraddr,
+    // Read port
+    input rdclk,
+    input rden,
+    input [5:0] rdaddr,
+    output reg [7:0] do);
+
+    (* syn_ramstyle = "block_ram" *) reg [7:0] ram[0:63];
+
+    initial begin
+        ram[0] = 8'b00000001;
+        ram[1] = 8'b10101010;
+        ram[2] = 8'b01010101;
+        ram[3] = 8'b11111111;
+        ram[4] = 8'b11110000;
+        ram[5] = 8'b00001111;
+        ram[6] = 8'b11001100;
+        ram[7] = 8'b00110011;
+        ram[8] = 8'b00000010;
+        ram[9] = 8'b00000100;
+    end
+
+    always @ (posedge wrclk) begin
+        if(wren == 1) begin
+            ram[wraddr] <= di;
+        end
+    end
+
+    always @ (posedge rdclk) begin
+        if(rden == 1) begin
+            do <= ram[rdaddr];
+        end
+    end
+
+endmodule
+
+module top (
+    input  wire clk,
+
+    input wire  pb0,
+    input wire  pb1,
+
+    input  wire [7:0] sw,
+    output wire [13:0] led
+);
+    wire bufclk;
+    DCC gbuf_i(.CLKI(clk), .CLKO(bufclk));
+
+
+    wire rden;
+    reg wren;
+    wire [5:0] rdaddr;
+    wire [5:0] wraddr;
+    wire [7:0] di;
+    wire [7:0] do;
+    ram0 ram(
+        .wrclk(bufclk),
+        .di(di),
+        .wren(wren),
+        .wraddr(wraddr),
+        .rdclk(bufclk),
+        .rden(rden),
+        .rdaddr(rdaddr),
+        .do(do)
+    );
+
+    reg [5:0] address_reg;
+    reg [7:0] data_reg;
+    reg [7:0] out_reg;
+
+    assign rdaddr = address_reg;
+    assign wraddr = address_reg;
+
+    // input_mode == 00 -> in[3:0] -> address_reg
+    // input_mode == 01 -> in[3:0] -> data_reg[3:0]
+    // input_mode == 10 -> in[3:0] -> data_reg[7:4]
+    // input_mode == 11 -> data_reg -> ram[address_reg]
+    wire [1:0] input_mode;
+
+    // WE == 0 -> address_reg and data_reg unchanged.
+    // WE == 1 -> address_reg or data_reg is updated because on input_mode.
+    wire we;
+
+    assign input_mode[0] = ~sw[6];
+    assign input_mode[1] = ~sw[7];
+
+    assign we = ~pb0;
+    assign led = ~{address_reg, out_reg};
+    assign di = data_reg;
+    assign rden = 1;
+
+    initial begin
+        wren = 1'b0;
+        address_reg = 10'b0;
+        data_reg = 16'b0;
+        out_reg = 16'b0;
+    end
+
+    always @ (posedge bufclk) begin
+        out_reg <= do;
+
+        if(we == 1) begin
+            if(input_mode == 0) begin
+                address_reg <= ~sw[5:0];
+                wren <= 0;
+            end else if(input_mode == 1) begin
+                data_reg[3:0] <= ~sw[3:0];
+                wren <= 0;
+            end else if(input_mode == 2) begin
+                data_reg[7:4] <= ~sw[3:0];
+                wren <= 0;
+            end else if(input_mode == 3) begin
+                wren <= 1;
+            end
+        end
+    end
+
+endmodule
diff --git a/fpga_interchange/examples/tests/ram_nexus/run_nexus.tcl b/fpga_interchange/examples/tests/ram_nexus/run_nexus.tcl
new file mode 100644
index 00000000..4ea5e282
--- /dev/null
+++ b/fpga_interchange/examples/tests/ram_nexus/run_nexus.tcl
@@ -0,0 +1,15 @@
+yosys -import
+
+read_verilog $::env(SOURCES)
+
+synth_nexus -nolutram -nowidelut -noccu2 -nodsp
+techmap -max_iter 1 -map $::env(TECHMAP)
+
+# opt_expr -undriven makes sure all nets are driven, if only by the $undef
+# net.
+opt_expr -undriven
+opt_clean
+
+setundef -zero -params
+
+write_json $::env(OUT_JSON)