lab-08: fix HiZ on register file when READ=0

Gate level implementation for the following components:
- DECODER_5x32
- MUX32_32x1
- REGISTER_FILE_32x32

Additional tests added in register file testbench.

TESTBENCH/register_file_tb.v

@@ -114,7 +114,6 @@ no_of_pass  = no_of_pass + 1;
 result[ridx] = DATA_R1; ridx=ridx+1;
 
 // TODO: Read and write from the same address at the same time?
-// TODO: Write when WRITE=0 should be tested
 
 #5    READ=1'b0; WRITE=1'b0; // No op
 

alu.v

@@ -44,7 +44,7 @@ wire [31:0] res,
 // can use oprn[1] or oprn[3] for SnA
 wire SnA;
 or (SnA, OPRN[1], OPRN[3]);
-RC_ADD_SUB_32 addsub(.Y(res_addsub), .CO(), .A(OP1), .B(OP2), .SnA(SnA));
+RC_ADD_SUB_32 addsub(.Y(res_addsub), .A(OP1), .B(OP2), .SnA(SnA));
 buf slt [31:0] (res_slt, {31'b0,res_addsub[31]});
 
 // shift_r = xx0100
@@ -54,7 +54,7 @@ buf slt [31:0] (res_slt, {31'b0,res_addsub[31]});
 SHIFT32 shift(res_shift, OP1, OP2, OPRN[0]);
 
 // mul = xx0011
-MULT32 mul(.LO(res_mul), .HI(), .A(OP1), .B(OP2));
+MULT32 mul(.LO(res_mul), .A(OP1), .B(OP2));
 
 // and = xx0110
 // or  = xx0111
@@ -63,12 +63,11 @@ AND32_2x1 and32(res_and, OP1, OP2);
 OR32_2x1 or32(res_or, OP1, OP2);
 NOR32_2x1 nor32(res_nor, OP1, OP2);
 
-MUX32_16x1 out(.Y(res), .S(OPRN[3:0]), .I0(),
+MUX32_16x1 out(.Y(res), .S(OPRN[3:0]),
                .I1(res_addsub), .I2(res_addsub), .I3(res_mul),
                .I4(res_shift),.I5(res_shift),
                .I6(res_and), .I7(res_or), .I8(res_nor),
-               .I9(res_slt),
-               .I10(), .I11(), .I12(), .I13(), .I14(), .I15()
+               .I9(res_slt)
 );
 
 // or bits of result for zero flag

logic.v

@@ -20,7 +20,7 @@ output [63:0] Y;
 //input list
 input [63:0] A;
 
-RC_ADD_SUB_64 twoscomp64_sub(.Y(Y), .CO(), .A(64'b0), .B(A), .SnA(1'b1));
+RC_ADD_SUB_64 twoscomp64_sub(.Y(Y), .A(64'b0), .B(A), .SnA(1'b1));
 
 endmodule
 
@@ -31,31 +31,7 @@ output [31:0] Y;
 //input list
 input [31:0] A;
 
-RC_ADD_SUB_32 twoscomp32_sub(.Y(Y), .CO(), .A(0), .B(A), .SnA(1'b1));
-
-endmodule
-
-// 32-bit register with parameterized preset pattern
-module REG32_PP(Q, D, LOAD, CLK, RESET);
-parameter PATTERN = 32'h00000000;
-output [31:0] Q;
-
-input CLK, LOAD;
-input [31:0] D;
-input RESET;
-
-wire [31:0] qbar;
-
-genvar i;
-generate
-    for(i=0; i<32; i=i+1)
-    begin : reg32_gen_loop
-       if (PATTERN[i] == 0)
-              REG1 reg_inst(.Q(Q[i]), .Qbar(qbar[i]), .D(D[i]), .L(LOAD), .C(CLK), .nP(1'b1), .nR(RESET));
-        else
-              REG1 reg_inst(.Q(Q[i]), .Qbar(qbar[i]), .D(D[i]), .L(LOAD), .C(CLK), .nP(RESET), .nR(1'b1));
-    end
-endgenerate
+RC_ADD_SUB_32 twoscomp32_sub(.Y(Y), .A(0), .B(A), .SnA(1'b1));
 
 endmodule
 

register_file.v

@@ -42,11 +42,8 @@ output [`DATA_INDEX_LIMIT:0] DATA_R1;
 output [`DATA_INDEX_LIMIT:0] DATA_R2;
 
 wire [31:0] Q [31:0];
-wire [31:0] r_write_sel, r_write;
-DECODER_5x32 d_write(r_write_sel, ADDR_W);
-
-// only write when WRITE=1
-and write_active [31:0] (r_write, r_write_sel, WRITE);
+wire [31:0] r_write;
+DECODER_5x32 d_write(r_write, ADDR_W);
 
 REG32 r[31:0] (Q, DATA_W, r_write, CLK, RST);