add: virtual DAC (100%) and ADC (80%)

upd: makefile

designs/reflectometer_base/dac_model.sv

@@ -0,0 +1,60 @@
+// AN9767 model (1 port)
+
+module virtual_dac_model #(
+    parameter int unsigned DAC_DATA_WIDTH = 14,
+
+    // Bipolar output range: +/- VOLTAGE_RANGE
+    parameter real VOLTAGE_RANGE = 5.0,
+
+    // Analog output correction
+    parameter real VOLTAGE_GAIN  = 1.0,
+    parameter real GROUND_BIAS   = 0.0,
+
+    // DAC timing parameters
+    parameter time TRANSMISSION_DELAY = 150ps,
+    parameter time CONVERSION_DELAY   = 150ps
+)(
+    input  logic                      clk_i,
+    input  logic                      wrt_i,
+    input  logic [DAC_DATA_WIDTH-1:0] data_i,
+
+    output real                       voltage_o
+);
+
+    localparam int unsigned ZERO_CODE = (1 << (DAC_DATA_WIDTH - 1));
+    localparam real VOLTAGE_STEP = VOLTAGE_RANGE / real'(ZERO_CODE);
+
+    logic [DAC_DATA_WIDTH-1:0] dac_code;
+
+    //------------------------------------------------------------
+    // Convert DAC code to analog voltage
+    //------------------------------------------------------------
+    function automatic real code_to_voltage( input logic [DAC_DATA_WIDTH-1:0] code);
+        return (int'(code) - int'(ZERO_CODE)) * VOLTAGE_STEP;
+    endfunction
+
+    //------------------------------------------------------------
+    // Initial state
+    //------------------------------------------------------------
+    initial begin
+        dac_code  = '0;
+        voltage_o = code_to_voltage('0) * VOLTAGE_GAIN + GROUND_BIAS;
+    end
+
+    //------------------------------------------------------------
+    // Latch new DAC code
+    //------------------------------------------------------------
+    always @(posedge wrt_i) begin
+        #(TRANSMISSION_DELAY);
+        dac_code = data_i;
+    end
+
+    //------------------------------------------------------------
+    // Update analog output
+    //------------------------------------------------------------
+    always @(posedge clk_i) begin
+        #(CONVERSION_DELAY);
+        voltage_o = code_to_voltage(dac_code) * VOLTAGE_GAIN + GROUND_BIAS;
+    end
+
+endmodule