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instr_decoder.sv
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`ifndef _instr_decoder_vh_
`define _instr_decoder_vh_
`include "z80.vh"
// Give an instruction (in little-endian order) and its op_len
// (the instruction length without any operands), determine
// what its total length (including operands) should be, and
// what group it's in.
module instr_decoder(
input logic [31:0] instr,
input logic [1:0] op_len,
output logic [2:0] len,
output logic [7:0] group
);
always @(*) begin
if (op_len == 0) begin
group <= `INSN_GROUP_NEED_MORE_BYTES;
len <= 1;
end
if (op_len == 1) begin
case (instr[7:0])
8'h00: begin
group <= `INSN_GROUP_NOP;
len <= 1;
end
8'h01, 8'h11, 8'h21, 8'h31: begin
group <= `INSN_GROUP_LD_DD_NN;
len <= 3;
end
8'h02, 8'h12: begin
group <= `INSN_GROUP_LD_IND_BCDE_A;
len <= 1;
end
8'h03, 8'h13, 8'h23, 8'h33,
8'h0B, 8'h1B, 8'h2B, 8'h3B: begin
group <= `INSN_GROUP_INC_DEC_DD;
len <= 1;
end
8'h04, 8'h0C, 8'h14, 8'h1C, 8'h24, 8'h2C, 8'h3C,
8'h05, 8'h0D, 8'h15, 8'h1D, 8'h25, 8'h2D, 8'h3D: begin
group <= `INSN_GROUP_INC_DEC_REG;
len <= 1;
end
8'h07, 8'h17, 8'h0F, 8'h1F: begin
group <= `INSN_GROUP_RR_RLCA;
len <= 1;
end
8'h09, 8'h19, 8'h29, 8'h39: begin
group <= `INSN_GROUP_ADD_HL_DD;
len <= 1;
end
8'h27: begin
group <= `INSN_GROUP_DAA;
len <= 1;
end
8'h2F: begin
group <= `INSN_GROUP_CPL;
len <= 1;
end
8'h34, 8'h35: begin
group <= `INSN_GROUP_INC_DEC_IND_HL;
len <= 1;
end
8'h0A, 8'h1A: begin
group <= `INSN_GROUP_LD_A_IND_BCDE;
len <= 1;
end
8'h06, 8'h0E, 8'h16, 8'h1E, 8'h26, 8'h2E, 8'h3E: begin
group <= `INSN_GROUP_LD_REG_N;
len <= 2;
end
8'h22: begin
group <= `INSN_GROUP_LD_IND_NN_HL;
len <= 3;
end
8'h2A: begin
group <= `INSN_GROUP_LD_HL_IND_NN;
len <= 3;
end
8'h36: begin
group <= `INSN_GROUP_LD_IND_HL_N;
len <= 2;
end
8'h7F, 8'h78, 8'h79, 8'h7A, 8'h7B, 8'h7C, 8'h7D,
8'h47, 8'h40, 8'h41, 8'h42, 8'h43, 8'h44, 8'h45,
8'h4F, 8'h48, 8'h49, 8'h4A, 8'h4B, 8'h4C, 8'h4D,
8'h57, 8'h50, 8'h51, 8'h52, 8'h53, 8'h54, 8'h55,
8'h5F, 8'h58, 8'h59, 8'h5A, 8'h5B, 8'h5C, 8'h5D,
8'h67, 8'h60, 8'h61, 8'h62, 8'h63, 8'h64, 8'h65,
8'h6F, 8'h68, 8'h69, 8'h6A, 8'h6B, 8'h6C, 8'h6D: begin
group <= `INSN_GROUP_LD_REG_REG;
len <= 1;
end
8'h32: begin
group <= `INSN_GROUP_LD_IND_NN_A;
len <= 3;
end
8'h37: begin
group <= `INSN_GROUP_SCF;
len <= 1;
end
8'h3A: begin
group <= `INSN_GROUP_LD_A_IND_NN;
len <= 3;
end
8'h3F: begin
group <= `INSN_GROUP_CCF;
len <= 1;
end
8'h70, 8'h71, 8'h72, 8'h73, 8'h74, 8'h75, 8'h77: begin
group <= `INSN_GROUP_LD_IND_HL_REG;
len <= 1;
end
8'h76: begin
group <= `INSN_GROUP_HALT;
len <= 1;
end
8'hC3: begin
group <= `INSN_GROUP_JP;
len <= 3;
end
8'b11???010: begin
group <= `INSN_GROUP_JP_COND;
len <= 3;
end
8'hE9: begin
group <= `INSN_GROUP_JP_IND_HL;
len <= 1;
end
8'h18: begin
group <= `INSN_GROUP_JR;
len <= 2;
end
8'b001??000: begin
group <= `INSN_GROUP_JR_COND;
len <= 2;
end
8'h10: begin
group <= `INSN_GROUP_DJNZ;
len <= 2;
end
8'hCD: begin
group <= `INSN_GROUP_CALL;
len <= 3;
end
8'b11???100: begin
group <= `INSN_GROUP_CALL_COND;
len <= 3;
end
8'hC9: begin
group <= `INSN_GROUP_RET;
len <= 1;
end
8'b11???000: begin
group <= `INSN_GROUP_RET_COND;
len <= 1;
end
8'b11???111: begin
group <= `INSN_GROUP_RST;
len <= 1;
end
8'hC1, 8'hD1, 8'hE1, 8'hF1: begin
group <= `INSN_GROUP_POP_QQ;
len <= 1;
end
8'hC5, 8'hD5, 8'hE5, 8'hF5: begin
group <= `INSN_GROUP_PUSH_QQ;
len <= 1;
end
8'h08: begin
group <= `INSN_GROUP_EX_AF_AF2;
len <= 1;
end
8'hE3: begin
group <= `INSN_GROUP_EX_IND_SP_HL;
len <= 1;
end
8'hEB: begin
group <= `INSN_GROUP_EX_DE_HL;
len <= 1;
end
8'hD9: begin
group <= `INSN_GROUP_EXX;
len <= 1;
end
8'hF9: begin
group <= `INSN_GROUP_LD_SP_HL;
len <= 1;
end
8'h80, 8'h81, 8'h82, 8'h83, 8'h84, 8'h85, 8'h87,
8'h88, 8'h89, 8'h8A, 8'h8B, 8'h8C, 8'h8D, 8'h8F,
8'h90, 8'h91, 8'h92, 8'h93, 8'h94, 8'h95, 8'h97,
8'h98, 8'h99, 8'h9A, 8'h9B, 8'h9C, 8'h9D, 8'h9F,
8'hA0, 8'hA1, 8'hA2, 8'hA3, 8'hA4, 8'hA5, 8'hA7,
8'hA8, 8'hA9, 8'hAA, 8'hAB, 8'hAC, 8'hAD, 8'hAF,
8'hB0, 8'hB1, 8'hB2, 8'hB3, 8'hB4, 8'hB5, 8'hB7,
8'hB8, 8'hB9, 8'hBA, 8'hBB, 8'hBC, 8'hBD, 8'hBF: begin
group <= `INSN_GROUP_ALU_A_REG;
len <= 1;
end
8'h86, 8'h8E, 8'h96, 8'h9E, 8'hA6, 8'hAE, 8'hB6, 8'hBE: begin
group <= `INSN_GROUP_ALU_A_IND_HL;
len <= 1;
end
8'hC6, 8'hCE, 8'hD6, 8'hDE, 8'hE6, 8'hEE, 8'hF6, 8'hFE: begin
group <= `INSN_GROUP_ALU_A_N;
len <= 2;
end
8'hCB, 8'hDD, 8'hED, 8'hFD: begin
group <= `INSN_GROUP_NEED_MORE_BYTES;
len <= 2;
end
8'hF3, 8'hFB: begin
group <= `INSN_GROUP_EI_DI;
len <= 1;
end
8'hD3: begin
group <= `INSN_GROUP_OUT_A;
len <= 2;
end
8'hDB: begin
group <= `INSN_GROUP_IN_A;
len <= 2;
end
default: begin
group <= `INSN_GROUP_ILLEGAL_INSTR;
len <= 1;
end
endcase
end else begin
case (instr[15:0])
16'h00CB, 16'h01CB, 16'h02CB, 16'h03CB,
16'h04CB, 16'h05CB, 16'h07CB,
16'h08CB, 16'h09CB, 16'h0ACB, 16'h0BCB,
16'h0CCB, 16'h0DCB, 16'h0FCB,
16'h10CB, 16'h11CB, 16'h12CB, 16'h13CB,
16'h14CB, 16'h15CB, 16'h17CB,
16'h18CB, 16'h19CB, 16'h1ACB, 16'h1BCB,
16'h1CCB, 16'h1DCB, 16'h1FCB: begin
group <= `INSN_GROUP_RR_RLC_REG;
len <= 2;
end
16'h06CB, 16'h16CB, 16'h0ECB, 16'h1ECB: begin
group <= `INSN_GROUP_RR_RLC_IND_HL;
len <= 2;
end
16'h20CB, 16'h21CB, 16'h22CB, 16'h23CB,
16'h24CB, 16'h25CB, 16'h27CB,
16'h28CB, 16'h29CB, 16'h2ACB, 16'h2BCB,
16'h2CCB, 16'h2DCB, 16'h2FCB,
16'h38CB, 16'h39CB, 16'h3ACB, 16'h3BCB,
16'h3CCB, 16'h3DCB, 16'h3FCB: begin
group <= `INSN_GROUP_SHIFT_REG;
len <= 2;
end
16'h26CB, 16'h2ECB, 16'h3ECB: begin
group <= `INSN_GROUP_SHIFT_IND_HL;
len <= 2;
end
16'b01???00011001011,
16'b01???00111001011,
16'b01???01011001011,
16'b01???01111001011,
16'b01???10011001011,
16'b01???10111001011,
16'b01???11111001011: begin
group <= `INSN_GROUP_BIT_REG;
len <= 2;
end
16'b01???11011001011: begin
group <= `INSN_GROUP_BIT_IND_HL;
len <= 2;
end
16'b11???00011001011,
16'b11???00111001011,
16'b11???01011001011,
16'b11???01111001011,
16'b11???10011001011,
16'b11???10111001011,
16'b11???11111001011: begin
group <= `INSN_GROUP_SET_REG;
len <= 2;
end
16'b11???11011001011: begin
group <= `INSN_GROUP_SET_IND_HL;
len <= 2;
end
16'b10???00011001011,
16'b10???00111001011,
16'b10???01011001011,
16'b10???01111001011,
16'b10???10011001011,
16'b10???10111001011,
16'b10???11111001011: begin
group <= `INSN_GROUP_RES_REG;
len <= 2;
end
16'b10???11011001011: begin
group <= `INSN_GROUP_RES_IND_HL;
len <= 2;
end
16'h41ED, 16'h49ED, 16'h51ED, 16'h59ED,
16'h61ED, 16'h69ED, 16'h79ED: begin
group <= `INSN_GROUP_OUT_REG;
len <= 2;
end
16'h40ED, 16'h48ED, 16'h50ED, 16'h58ED,
16'h60ED, 16'h68ED, 16'h78ED: begin
group <= `INSN_GROUP_IN_REG;
len <= 2;
end
16'h42ED, 16'h52ED, 16'h62ED, 16'h72ED,
16'h4AED, 16'h5AED, 16'h6AED, 16'h7AED: begin
group <= `INSN_GROUP_ADC_SBC_HL_DD;
len <= 2;
end
16'h4BED, 16'h5BED, 16'h6BED, 16'h7BED: begin
group <= `INSN_GROUP_LD_DD_IND_NN;
len <= 4;
end
16'h44ED: begin
group <= `INSN_GROUP_NEG;
len <= 2;
end
16'h46ED, 16'h56ED, 16'h5EED: begin
group <= `INSN_GROUP_IM;
len <= 2;
end
16'h43ED, 16'h53ED, 16'h63ED, 16'h73ED: begin
group <= `INSN_GROUP_LD_IND_NN_DD;
len <= 4;
end
16'h45ED: begin
group <= `INSN_GROUP_RETN;
len <= 2;
end
16'h4DED: begin
group <= `INSN_GROUP_RETI;
len <= 2;
end
16'b101??011_11101101: begin
group <= `INSN_GROUP_OUT_BLOCK;
len <= 2;
end
16'b101??010_11101101: begin
group <= `INSN_GROUP_IN_BLOCK;
len <= 2;
end
16'h09DD, 16'h19DD, 16'h29DD, 16'h39DD,
16'h09FD, 16'h19FD, 16'h29FD, 16'h39FD: begin
group <= `INSN_GROUP_ADD_IXIY_SS;
len <= 2;
end
16'h23DD, 16'h2BDD, 16'h23FD, 16'h2BFD: begin
group <= `INSN_GROUP_INC_DEC_IXIY;
len <= 2;
end
16'h46DD, 16'h4EDD, 16'h56DD, 16'h5EDD,
16'h66DD, 16'h6EDD, 16'h7EDD,
16'h46FD, 16'h4EFD, 16'h56FD, 16'h5EFD,
16'h66FD, 16'h6EFD, 16'h7EFD: begin
group <= `INSN_GROUP_LD_REG_IDX_IXIY;
len <= 3;
end
16'h70DD, 16'h71DD, 16'h72DD, 16'h73DD,
16'h74DD, 16'h75DD, 16'h77DD,
16'h70FD, 16'h71FD, 16'h72FD, 16'h73FD,
16'h74FD, 16'h75FD, 16'h77FD: begin
group <= `INSN_GROUP_LD_IDX_IXIY_REG;
len <= 3;
end
16'h21DD, 16'h21FD: begin
group <= `INSN_GROUP_LD_IXIY_NN;
len <= 4;
end
16'h2ADD, 16'h2AFD: begin
group <= `INSN_GROUP_LD_IXIY_IND_NN;
len <= 4;
end
16'h34DD, 16'h34FD, 16'h35DD, 16'h35FD: begin
group <= `INSN_GROUP_INC_DEC_IDX_IXIY;
len <= 3;
end
16'h36DD, 16'h36FD: begin
group <= `INSN_GROUP_LD_IDX_IXIY_N;
len <= 4;
end
16'hE3DD, 16'hE3FD: begin
group <= `INSN_GROUP_EX_IND_SP_IXIY;
len <= 2;
end
16'hE1DD, 16'hE1FD: begin
group <= `INSN_GROUP_POP_IXIY;
len <= 2;
end
16'hE5DD, 16'hE5FD: begin
group <= `INSN_GROUP_PUSH_IXIY;
len <= 2;
end
16'h22DD, 16'h22FD: begin
group <= `INSN_GROUP_LD_IND_NN_IXIY;
len <= 4;
end
16'h86DD, 16'h8EDD, 16'h96DD, 16'h9EDD,
16'hA6DD, 16'hAEDD, 16'hB6DD, 16'hBEDD,
16'h86FD, 16'h8EFD, 16'h96FD, 16'h9EFD,
16'hA6FD, 16'hAEFD, 16'hB6FD, 16'hBEFD: begin
group <= `INSN_GROUP_ALU_A_IDX_IXIY;
len <= 3;
end
16'hE9DD, 16'hE9FD: begin
group <= `INSN_GROUP_JP_IND_IXIY;
len <= 2;
end
16'h47ED: begin
group <= `INSN_GROUP_LD_I_A;
len <= 2;
end
16'h4FED: begin
group <= `INSN_GROUP_LD_R_A;
len <= 2;
end
16'h57ED: begin
group <= `INSN_GROUP_LD_A_I;
len <= 2;
end
16'h5FED: begin
group <= `INSN_GROUP_LD_A_R;
len <= 2;
end
16'h67ED, 16'h6FED: begin
group <= `INSN_GROUP_ROT_DEC;
len <= 2;
end
16'hF9DD, 16'hF9FD: begin
group <= `INSN_GROUP_LD_SP_IXIY;
len <= 2;
end
16'hA0ED: begin
group <= `INSN_GROUP_LDI;
len <= 2;
end
16'hA1ED: begin
group <= `INSN_GROUP_CPI;
len <= 2;
end
16'hA8ED: begin
group <= `INSN_GROUP_LDD;
len <= 2;
end
16'hA9ED: begin
group <= `INSN_GROUP_CPD;
len <= 2;
end
16'hB0ED: begin
group <= `INSN_GROUP_LDIR;
len <= 2;
end
16'hB1ED: begin
group <= `INSN_GROUP_CPIR;
len <= 2;
end
16'hB8ED: begin
group <= `INSN_GROUP_LDDR;
len <= 2;
end
16'hB9ED: begin
group <= `INSN_GROUP_CPDR;
len <= 2;
end
16'hCBDD, 16'hCBFD: begin
// This group is a whole section where the next
// byte is the index offset, and the byte after
// that is the instruction.
group <= `INSN_GROUP_IDX_IXIY_BITS;
len <= 4;
end
default: begin
group <= `INSN_GROUP_ILLEGAL_INSTR;
len <= 2;
end
endcase
end
end
endmodule
// Give the fourth byte in an INSN_GROUP_IDX_IXIY_BITS
// instruction, determine what its IDX_IXIY group is.
module instr_ixiy_bits_decoder(
input logic [7:0] instr,
output logic [7:0] group
);
always @(*) begin
case (instr)
8'h06, 8'h16, 8'h0E, 8'h1E:
group <= `INSN_GROUP_RR_RLC_IDX_IXIY;
8'h26, 8'h2E, 8'h3E:
group <= `INSN_GROUP_SHIFT_IDX_IXIY;
8'b01???110:
group <= `INSN_GROUP_BIT_IDX_IXIY;
8'b11???110:
group <= `INSN_GROUP_SET_IDX_IXIY;
8'b10???110:
group <= `INSN_GROUP_RES_IDX_IXIY;
default:
group <= `INSN_GROUP_ILLEGAL_INSTR;
endcase
end
endmodule
`endif // _instr_decoder_vh_