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decode Aax and Abx

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This commit is contained in:
Raphael Jacquot 2019-03-05 07:56:33 +01:00
parent f12a74a917
commit 98b3ed1b79
2 changed files with 99 additions and 8 deletions
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9
saturn_def_alu.v
View file

@ -11,6 +11,15 @@
`define T_PTR_0 0
`define T_PTR_1 1
`define FT_NONE 0
`define FT_A_B 1
`define FT_F 2
`define FT_FIELD_P 0
`define FT_FIELD_NONE 14
`define FT_FIELD_A 15
/*
*
* Opcodes for the ALU

98
saturn_inst_decoder.v
View file

@ -41,6 +41,7 @@ module saturn_inst_decoder (
o_alu_reg_dest,
o_alu_reg_src_1,
o_alu_reg_src_2,
o_alu_field,
o_alu_ptr_begin,
o_alu_ptr_end,
o_alu_imm_value,
@ -77,6 +78,7 @@ output reg [19:0] o_instr_pc;
output reg [4:0] o_alu_reg_dest;
output reg [4:0] o_alu_reg_src_1;
output reg [4:0] o_alu_reg_src_2;
output reg [3:0] o_alu_field;
output reg [3:0] o_alu_ptr_begin;
output reg [3:0] o_alu_ptr_end;
output reg [3:0] o_alu_imm_value;
@ -136,7 +138,8 @@ reg [0:0] block_80Cx;
reg [0:0] block_82x;
reg [0:0] block_84x_85x;
reg [0:0] block_Ax;
reg [0:0] block_Axx;
reg [0:0] block_Aax;
reg [0:0] block_Abx;
reg [0:0] block_JUMP;
reg [0:0] block_LOAD;
@ -148,6 +151,7 @@ reg [0:0] block_FIELDS;
reg [2:0] jump_counter;
reg [3:0] load_counter;
reg [3:0] load_count;
reg [1:0] fields_table;
/*
* initialization
@ -157,6 +161,7 @@ initial begin
o_alu_reg_dest = `ALU_REG_NONE;
o_alu_reg_src_1 = `ALU_REG_NONE;
o_alu_reg_src_2 = `ALU_REG_NONE;
o_alu_field = `FT_FIELD_NONE;
o_alu_ptr_begin = 4'h0;
o_alu_ptr_end = 4'h0;
o_alu_imm_value = 4'b0;
@ -184,7 +189,8 @@ initial begin
block_82x = 1'b0;
block_84x_85x = 1'b0;
block_Ax = 1'b0;
block_Axx = 1'b0;
block_Aax = 1'b0;
block_Abx = 1'b0;
block_JUMP = 1'b0;
block_LOAD = 1'b0;
@ -194,6 +200,7 @@ initial begin
jump_counter = 3'd0;
load_counter = 4'd0;
load_count = 4'd0;
fields_table = `FT_NONE;
/* last line of defense */
o_decoder_error = 1'b0;
@ -250,6 +257,7 @@ always @(posedge i_clk) begin
begin
block_Ax <= 1'b1;
block_FIELDS <= 1'b1;
fields_table <= `FT_A_B;
end
default:
begin
@ -447,14 +455,23 @@ always @(posedge i_clk) begin
if (block_Ax) begin
$display("DECODER %0d: [%d] block_Ax %h", i_phase, i_cycle_ctr, i_nibble);
/* work here is done by the block_FIELDS */
block_Axx <= 1'b1;
block_Aax <= !i_nibble[3];
block_Abx <= i_nibble[3];
block_Ax <= 1'b0;
end
if (block_Axx) begin
$display("DECODER %0d: [%d] block_Axx %h", i_phase, i_cycle_ctr, i_nibble);
if (block_Aax) begin
$display("DECODER %0d: [%d] block_Aax %h (%0d [%h:%h])",
i_phase, i_cycle_ctr, i_nibble, o_alu_field, o_alu_ptr_end, o_alu_ptr_begin);
o_decoder_error <= 1'b1;
block_Axx <= 1'b0;
block_Aax <= 1'b0;
end
if (block_Abx) begin
$display("DECODER %0d: [%d] block_Abx %h (%0d [%h:%h])",
i_phase, i_cycle_ctr, i_nibble, o_alu_field, o_alu_ptr_end, o_alu_ptr_begin);
o_decoder_error <= 1'b1;
block_Abx <= 1'b0;
end
/* special cases */
@ -481,6 +498,67 @@ always @(posedge i_clk) begin
if (block_FIELDS) begin
$display("DECODER %0d: [%d] block_FIELDS %h", i_phase, i_cycle_ctr, i_nibble);
o_alu_field <= { 1'b0, i_nibble[2:0] };
case (i_nibble[2:0])
3'o0:
begin
/* field pointed by P */
o_alu_ptr_begin <= i_reg_p;
o_alu_ptr_end <= i_reg_p;
end
3'o1:
begin
/* field the width of P, starting at 0 */
o_alu_ptr_begin <= 4'h0;
o_alu_ptr_end <= i_reg_p;
end
3'o2:
begin
/* field XS */
o_alu_ptr_begin <= 4'h2;
o_alu_ptr_end <= 4'h2;
end
3'o3:
begin
/* field X */
o_alu_ptr_begin <= 4'h0;
o_alu_ptr_end <= 4'h2;
end
3'o4:
begin
/* field S */
o_alu_ptr_begin <= 4'hF;
o_alu_ptr_end <= 4'hF;
end
3'o5:
begin
/* field M */
o_alu_ptr_begin <= 4'h3;
o_alu_ptr_end <= 4'hE;
end
3'o6:
begin
/* field B */
o_alu_ptr_begin <= 4'h0;
o_alu_ptr_end <= 4'h1;
end
3'o7:
begin
if ((fields_table == `FT_F) && i_nibble[3])
begin
/* this is field A */
o_alu_field <= i_nibble;
o_alu_ptr_begin <= 4'h0;
o_alu_ptr_end <= 4'h4;
end
else
begin
/* else this is field W */
o_alu_ptr_begin <= 4'h0;
o_alu_ptr_end <= 4'hF;
end
end
endcase
block_FIELDS <= 1'b0;
end
@ -495,7 +573,8 @@ always @(posedge i_clk) begin
/* decoder cleanup only after the instruction is completely decoded and execution has started */
if (i_phases[3] && o_instr_decoded) begin
// $display("DECODER %0d: [%d] decoder cleanup", i_phase, i_cycle_ctr);
fields_table <= `FT_NONE;
o_alu_field <= `FT_FIELD_NONE;
o_instr_decoded <= 1'b0;
o_instr_execute <= 1'b0;
o_instr_type <= `INSTR_TYPE_NONE;
@ -510,6 +589,7 @@ always @(posedge i_clk) begin
o_alu_reg_dest <= `ALU_REG_NONE;
o_alu_reg_src_1 <= `ALU_REG_NONE;
o_alu_reg_src_2 <= `ALU_REG_NONE;
o_alu_field <= `FT_FIELD_NONE;
o_alu_ptr_begin <= 4'h0;
o_alu_ptr_end <= 4'h0;
o_alu_imm_value <= 4'b0;
@ -537,7 +617,8 @@ always @(posedge i_clk) begin
block_82x <= 1'b0;
block_84x_85x <= 1'b0;
block_Ax <= 1'b0;
block_Axx <= 1'b0;
block_Aax <= 1'b0;
block_Abx <= 1'b0;
block_JUMP <= 1'b0;
block_LOAD <= 1'b0;
@ -547,6 +628,7 @@ always @(posedge i_clk) begin
jump_counter <= 3'd0;
load_counter <= 4'd0;
load_count <= 4'd0;
fields_table <= `FT_NONE;
/* invalid instruction */
o_decoder_error <= 1'b0;