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ALU,decoder: make combinatorial

master
Denis Tereshkin 1 month ago
parent
064b1c0727
commit
0dd5d0341a
4 changed files with 344 additions and 258 deletions
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  1. 88
      src/alu.verilog
  2. 258
      src/decoder.verilog
  3. 18
      src/parameters.vh
  4. 54
      tests/test_alu.verilog

88
src/alu.verilog
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@ -1,86 +1,84 @@ @@ -1,86 +1,84 @@
module alu
(
input nrst,
input clk,
input [7:0] A,
input [7:0] B,
input C,
input [2:0] sel,
output [7:0] result,
output r_n,
output r_z,
output reg r_v,
output reg r_c
input logic [7:0] A,
input logic [7:0] B,
input logic C,
input logic [2:0] sel,
output logic [7:0] result,
output logic r_n,
output logic r_z,
output logic r_v,
output logic r_c
);
wire rst = !nrst;
`include "parameters.vh"
reg [8:0] buffer;
wire [8:0] sum;
wire [8:0] diff;
assign result[7:0] = buffer[7:0];
assign r_z = buffer[7:0] == 0;
assign r_n = buffer[7];
assign sum = A + B + C;
assign diff = A - B - (1 - C);
initial begin
buffer <= 0;
r_v <= 0;
r_c <= 0;
end
assign r_z = result[7:0] == 0;
assign r_n = result[7];
assign sum = A + B + C;
assign diff = A - B - (1 - C);
always @(posedge clk)
always_comb
begin
case (sel)
OP_OR:
begin
buffer <= A | B;
result = A | B;
r_v = 0;
r_c = 0;
end
OP_AND:
begin
buffer <= A & B;
result = A & B;
r_v = 0;
r_c = 0;
end
OP_EOR:
begin
buffer <= A ^ B;
result = A ^ B;
r_v = 0;
r_c = 0;
end
OP_ADC:
begin
buffer <= sum;
r_c <= sum[8];
r_v <= !(A[7] ^ B[7]) & (A[7] & sum[7]);
result = sum[7:0];
r_c = sum[8];
r_v = !(A[7] ^ B[7]) & (A[7] ^ sum[7]);
end
OP_SUB:
begin
buffer <= diff;
r_c <= diff[8];
r_v <= !(A[7] ^ B[7]) & (A[7] & diff[7]);
result = diff;
r_c = diff[8];
r_v = !(A[7] ^ B[7]) & (A[7] ^ diff[7]);
end
OP_ROT:
begin
if (B == SHIFT_LEFT) begin
buffer[8:1] <= A[7:0];
buffer[0] <= C;
r_c <= A[7];
result[7:1] = A[6:0];
result[0] = C;
r_c = A[7];
end
else begin
buffer[6:0] <= A[7:1];
buffer[7] <= C;
r_c <= A[0];
result[6:0] = A[7:1];
result[7] = C;
r_c = A[0];
end
end
OP_SHF:
begin
if (B == SHIFT_LEFT) begin
buffer[8:1] <= A[7:0];
buffer[0] <= 0;
r_c <= A[7];
result[7:1] = A[6:0];
result[0] = 0;
r_c = A[7];
end
else begin
buffer[6:0] <= A[7:1];
buffer[7] <= 0;
r_c <= A[0];
result[6:0] = A[7:1];
result[7] = 0;
r_c = A[0];
end
end
endcase // case sel

258
src/decoder.verilog
Unescape View File

@ -4,8 +4,8 @@ module decoder @@ -4,8 +4,8 @@ module decoder
input clk,
input rst,
input [7:0] instr,
output reg [3:0] address_code,
output reg [7:0] decoded
output logic [4:0] address_code,
output logic [7:0] decoded
);
`include "parameters.vh"
@ -18,151 +18,225 @@ module decoder @@ -18,151 +18,225 @@ module decoder
wire sec_2_nop = (sector == 2) && ((column == 0 && (row == 4 || row == 6 || row == 7))
|| (column == 6 && (row != 4 && row != 5)));
always @* begin
always_comb begin
address_code = 0;
decoded = 0;
if (rst) begin
address_code <= 0;
address_code = 8'h0;
end
else begin
if (sector == 1) begin
case (row)
0: decoded <= I_ORA;
1: decoded <= I_AND;
2: decoded <= I_EOR;
3: decoded <= I_ADC;
4: decoded <= (column == 2 ? I_STA : I_NOP);
5: decoded <= I_LDA;
6: decoded <= I_CMP;
7: decoded <= I_SBC;
0: decoded = I_ORA;
1: decoded = I_AND;
2: decoded = I_EOR;
3: decoded = I_ADC;
4: decoded = (column == 2 ? I_STA : I_NOP);
5: decoded = I_LDA;
6: decoded = I_CMP;
7: decoded = I_SBC;
endcase
address_code <= column;
address_code = column;
end
else if (sector == 2) begin
case (row)
0: decoded <= (sec_2_stp ? I_STP : (sec_2_nop ? I_NOP : I_ASL));
1: decoded <= (sec_2_stp ? I_STP : (sec_2_nop ? I_NOP : I_ROL));
2: decoded <= (sec_2_stp ? I_STP : (sec_2_nop ? I_NOP : I_LSR));
3: decoded <= (sec_2_stp ? I_STP : (sec_2_nop ? I_NOP : I_ROR));
4: decoded <= (sec_2_stp ? I_STP : (sec_2_nop ? I_NOP : (column[0] ? I_STX : I_TXA)));
5: decoded <= (sec_2_stp ? I_STP : (column == 2 ? I_TAX : (column == 6 ? I_TSX : I_LDX)));
6: decoded <= (sec_2_stp ? I_STP : (sec_2_nop ? I_NOP : (column == 2 ? I_DEX : I_DEC)));
7: decoded <= (sec_2_stp ? I_STP : ((sec_2_nop || column == 2) ? I_NOP : I_INC));
0: decoded = (sec_2_stp ? I_STP : (sec_2_nop ? I_NOP : I_ASL));
1: decoded = (sec_2_stp ? I_STP : (sec_2_nop ? I_NOP : I_ROL));
2: decoded = (sec_2_stp ? I_STP : (sec_2_nop ? I_NOP : I_LSR));
3: decoded = (sec_2_stp ? I_STP : (sec_2_nop ? I_NOP : I_ROR));
4: decoded = (sec_2_stp ? I_STP : (sec_2_nop ? I_NOP : (column[0] ? I_STX : I_TXA)));
5: decoded = (sec_2_stp ? I_STP : (column == 2 ? I_TAX : (column == 6 ? I_TSX : I_LDX)));
6: decoded = (sec_2_stp ? I_STP : (sec_2_nop ? I_NOP : (column == 2 ? I_DEX : I_DEC)));
7: decoded = (sec_2_stp ? I_STP : ((sec_2_nop || column == 2) ? I_NOP : I_INC));
endcase
if (column > 0) begin
address_code <= column
address_code = column;
end
else begin
address_code <= ADDR_MODE_IMMEDIATE;
address_code = ADDR_MODE_IMMEDIATE;
end
end
else if (sector == 0) begin
if (column == 0) begin
case (row)
0: decoded <= I_BRK;
1: decoded <= I_JSR;
2: decoded <= I_RTI;
3: decoded <= I_RTS;
4: decoded <= I_NOP;
5: decoded <= I_LDY;
6: decoded <= I_CPY;
7: decoded <= I_CPX;
0: decoded = I_BRK;
1: decoded = I_JSR;
2: decoded = I_RTI;
3: decoded = I_RTS;
4: decoded = I_NOP;
5: decoded = I_LDY;
6: decoded = I_CPY;
7: decoded = I_CPX;
endcase
end
else if (column == 1) begin
case (row)
0: decoded <= I_NOP;
1: decoded <= I_BIT;
2: decoded <= I_NOP;
3: decoded <= I_NOP;
4: decoded <= I_STY;
5: decoded <= I_LDY;
6: decoded <= I_CPY;
7: decoded <= I_CPX;
0: decoded = I_NOP;
1: decoded = I_BIT;
2: decoded = I_NOP;
3: decoded = I_NOP;
4: decoded = I_STY;
5: decoded = I_LDY;
6: decoded = I_CPY;
7: decoded = I_CPX;
endcase
end
else if (column == 2) begin
case (row)
0: decoded <= I_PHP;
1: decoded <= I_PLP;
2: decoded <= I_PHA;
3: decoded <= I_PLA;
4: decoded <= I_DEY;
5: decoded <= I_TAY;
6: decoded <= I_INY;
7: decoded <= I_INX;
0: decoded = I_PHP;
1: decoded = I_PLP;
2: decoded = I_PHA;
3: decoded = I_PLA;
4: decoded = I_DEY;
5: decoded = I_TAY;
6: decoded = I_INY;
7: decoded = I_INX;
endcase
end
else if (column == 3) begin
case (row)
0: decoded <= I_NOP;
1: decoded <= I_BIT;
2: decoded <= I_JMP;
3: decoded <= I_JMP;
4: decoded <= I_STY;
5: decoded <= I_LDY;
6: decoded <= I_CPY;
7: decoded <= I_CPX;
0: decoded = I_NOP;
1: decoded = I_BIT;
2: decoded = I_JMP;
3: decoded = I_JMP;
4: decoded = I_STY;
5: decoded = I_LDY;
6: decoded = I_CPY;
7: decoded = I_CPX;
endcase
end
else if (column == 4) begin
case (row)
0: decoded <= I_BPL;
1: decoded <= I_BMI;
2: decoded <= I_BVC;
3: decoded <= I_BVS;
4: decoded <= I_BCC;
5: decoded <= I_BCS;
6: decoded <= I_BNE;
7: decoded <= I_BEQ;
0: decoded = I_BPL;
1: decoded = I_BMI;
2: decoded = I_BVC;
3: decoded = I_BVS;
4: decoded = I_BCC;
5: decoded = I_BCS;
6: decoded = I_BNE;
7: decoded = I_BEQ;
endcase
end
else if (column == 5) begin
case (row)
0: decoded <= I_NOP;
1: decoded <= I_NOP;
2: decoded <= I_NOP;
3: decoded <= I_NOP;
4: decoded <= I_STY;
5: decoded <= I_LDY;
6: decoded <= I_NOP;
7: decoded <= I_NOP;
0: decoded = I_NOP;
1: decoded = I_NOP;
2: decoded = I_NOP;
3: decoded = I_NOP;
4: decoded = I_STY;
5: decoded = I_LDY;
6: decoded = I_NOP;
7: decoded = I_NOP;
endcase
end
else if (column == 6) begin
case (row)
0: decoded <= I_CLC;
1: decoded <= I_SEC;
2: decoded <= I_CLI;
3: decoded <= I_SEI;
4: decoded <= I_TYA;
5: decoded <= I_CLV;
6: decoded <= I_CLD;
7: decoded <= I_SED;
0: decoded = I_CLC;
1: decoded = I_SEC;
2: decoded = I_CLI;
3: decoded = I_SEI;
4: decoded = I_TYA;
5: decoded = I_CLV;
6: decoded = I_CLD;
7: decoded = I_SED;
endcase
end
else if (column == 7) begin
case (row)
0: decoded <= I_NOP;
1: decoded <= I_NOP;
2: decoded <= I_NOP;
3: decoded <= I_NOP;
4: decoded <= I_SHY;
5: decoded <= I_LDY;
6: decoded <= I_NOP;
7: decoded <= I_NOP;
0: decoded = I_NOP;
1: decoded = I_NOP;
2: decoded = I_NOP;
3: decoded = I_NOP;
4: decoded = I_SHY;
5: decoded = I_LDY;
6: decoded = I_NOP;
7: decoded = I_NOP;
endcase
end
end
if (column > 0) begin
address_code <= column;
if (sector == 0) begin
if (column == 0) begin
if (row == 0 || (row >= 2 && row <= 4)) begin
address_code = ADDR_MODE_IMPLIED;
end
else if (row == 1) begin
address_code = ADDR_MODE_ABSOLUTE;
end
else begin
if (row >= 4) begin
address_code <= ADDR_MODE_IMMEDIATE;
address_code = ADDR_MODE_IMMEDIATE;
end
end
else if(column == 1) begin
address_code = ADDR_MODE_ZP;
end
else if (column == 2) begin
address_code = ADDR_MODE_IMPLIED;
end
else if (column == 3) begin
if (row == 3) begin
address_code = ADDR_MODE_ABSOLUTE;
end
else begin
address_code <= ADDR_MODE_ABSOLUTE;
address_code = ADDR_MODE_INDEXED_ABSOLUTE;
end
end
else if (column == 4) begin
address_code = ADDR_MODE_RELATIVE;
end
else if (column == 5) begin
address_code = ADDR_MODE_INDEXED_ZP;
end
else if (column == 6) begin
address_code = ADDR_MODE_IMPLIED;
end
else if (column == 7) begin
address_code = ADDR_MODE_INDEXED_ABSOLUTE;
end
end
else if(sector == 1) begin
if (column == 0) begin
address_code = ADDR_MODE_PREINDEXED_INDIRECT;
end
else if (column == 1) begin
address_code = ADDR_MODE_ZP;
end
else if (column == 2) begin
address_code = ADDR_MODE_IMMEDIATE;
end
else if (column == 3) begin
address_code = ADDR_MODE_ABSOLUTE;
end
else if (column == 4) begin
address_code = ADDR_MODE_POSTINDEXED_INDIRECT;
end
else if (column == 5) begin
address_code = ADDR_MODE_INDEXED_ZP;
end
else if (column == 6 || column == 7) begin
address_code = ADDR_MODE_INDEXED_ABSOLUTE;
end
end
else if(sector == 2) begin
if (column == 0) begin
address_code = ADDR_MODE_IMMEDIATE;
end
else if (column == 1) begin
address_code = ADDR_MODE_ZP;
end
else if (column == 2 || column == 6) begin
address_code = ADDR_MODE_IMPLIED;
end
else if (column == 3) begin
address_code = ADDR_MODE_ABSOLUTE;
end
// column == 4 are invalid opcodes
else if (column == 5) begin
address_code = ADDR_MODE_INDEXED_ZP;
end
else if (column == 7) begin
address_code = ADDR_MODE_INDEXED_ABSOLUTE;
end
end
end

18
src/parameters.vh
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@ -1,12 +1,14 @@ @@ -1,12 +1,14 @@
parameter ADDR_MODE_INDEXED_INDIRECT = 0;
parameter ADDR_MODE_ZP = 1;
parameter ADDR_MODE_IMMEDIATE = 2;
parameter ADDR_MODE_ABSOLUTE = 3;
parameter ADDR_MODE_INDIRECT_INDEXED = 4;
parameter ADDR_MODE_ZP_X = 5;
parameter ADDR_MODE_ABS_Y = 6;
parameter ADDR_MODE_ABS_X = 7;
parameter ADDR_MODE_IMPLIED = 0;
parameter ADDR_MODE_IMMEDIATE = 1;
parameter ADDR_MODE_ABSOLUTE = 2;
parameter ADDR_MODE_ZP = 3;
parameter ADDR_MODE_INDEXED_ABSOLUTE = 4;
parameter ADDR_MODE_INDEXED_ZP = 5;
parameter ADDR_MODE_INDIRECT = 6;
parameter ADDR_MODE_PREINDEXED_INDIRECT = 7;
parameter ADDR_MODE_POSTINDEXED_INDIRECT = 8;
parameter ADDR_MODE_RELATIVE = 9;
parameter OP_OR = 0;
parameter OP_AND = 1;

54
tests/test_alu.verilog
Unescape View File

@ -1,8 +1,8 @@ @@ -1,8 +1,8 @@
module test_alu;
initial begin
initial begin
$dumpfile("test.vcd");
$dumpvars(0, test_alu);
end
end
`define assert(signal, value) \
if (signal !== value) begin \
@ -11,9 +11,6 @@ if (signal !== value) begin \ @@ -11,9 +11,6 @@ if (signal !== value) begin \
end
reg nrst = 1;
reg clk = 0;
reg [7:0] A;
reg [7:0] B;
reg C;
@ -25,11 +22,9 @@ if (signal !== value) begin \ @@ -25,11 +22,9 @@ if (signal !== value) begin \
wire r_c;
wire r_v;
always #1 clk = !clk;
`include "parameters.vh"
alu my_alu(
.nrst(nrst),
.clk(clk),
alu my_alu(
.A(A),
.B(B),
.C(C),
@ -40,19 +35,23 @@ if (signal !== value) begin \ @@ -40,19 +35,23 @@ if (signal !== value) begin \
.r_c(r_c),
.r_v(r_v));
initial begin
initial begin
// Testing OR
#10 A = 8'h11;
B = 8'h22;
C = 0;
op_sel = 0; // OR
op_sel = OP_OR;
#2 `assert (result, 8'h33);
#2 op_sel = 1; // AND
// Testing AND
#2 op_sel = OP_AND;
#2 `assert (result, 8'h00);
#2 op_sel = 2; // EOR
// Testing EOR
#2 op_sel = OP_EOR;
#2 `assert (result, 8'h33);
@ -61,14 +60,18 @@ if (signal !== value) begin \ @@ -61,14 +60,18 @@ if (signal !== value) begin \
#2 `assert (result, 8'h00);
#2 op_sel = 3; // ADC
// Testing ADC
// Without carry
#2 op_sel = OP_ADC;
#2 A = 8'h22;
B = 8'h22;
C = 0;
#2 `assert (result, 8'h44);
#2 C = 1; // ADD with CARRY
// With carry
#2 C = 1;
#2 `assert (result, 8'h45);
@ -78,7 +81,8 @@ if (signal !== value) begin \ @@ -78,7 +81,8 @@ if (signal !== value) begin \
#2 `assert (r_c, 1);
#2 op_sel = 4;
// Test SUB
#2 op_sel = OP_SUB;
A = 8'hf0;
B = 8'h10;
C = 0;
@ -88,10 +92,11 @@ if (signal !== value) begin \ @@ -88,10 +92,11 @@ if (signal !== value) begin \
#2 `assert (result, 8'he0);
#2 op_sel = 5;
// Test ROT
#2 op_sel = OP_ROT;
A = 8'hf0;
B = 8'h00;
B = SHIFT_LEFT;
C = 1;
#2 `assert (result, 8'he1);
@ -101,7 +106,7 @@ if (signal !== value) begin \ @@ -101,7 +106,7 @@ if (signal !== value) begin \
#2 `assert (result, 8'he0);
#2 B = 1;
#2 B = SHIFT_RIGHT;
C = 0;
#2 `assert (result, 8'h78);
@ -112,9 +117,16 @@ if (signal !== value) begin \ @@ -112,9 +117,16 @@ if (signal !== value) begin \
#2 `assert (result, 8'hf8);
`assert (r_c, 1);
#2 op_sel = 6;
// Test SHF
#2 op_sel = OP_SHF;
A = 8'hf9;
B = SHIFT_LEFT;
#1 `assert (result, 8'hf2);
B = SHIFT_RIGHT;
#1 `assert (result, 8'h7c);
#500 $finish;
end
end
endmodule

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