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--------------------------------------------------------------------- -- TITLE: Controller / Opcode Decoder -- AUTHOR: Steve Rhoads (rhoadss@yahoo.com) -- DATE CREATED: 2/8/01 -- FILENAME: control.vhd -- PROJECT: Plasma CPU core -- COPYRIGHT: Software placed into the public domain by the author. -- Software 'as is' without warranty. Author liable for nothing. -- NOTE: MIPS(tm) is a registered trademark of MIPS Technologies. -- MIPS Technologies does not endorse and is not associated with -- this project. -- DESCRIPTION: -- Controls the CPU by decoding the opcode and generating control -- signals to the rest of the CPU. -- This entity decodes the MIPS(tm) opcode into a -- Very-Long-Word-Instruction. -- The 32-bit opcode is converted to a -- 6+6+6+16+4+2+4+3+2+2+3+2+4 = 60 bit VLWI opcode. -- Based on information found in: -- "MIPS RISC Architecture" by Gerry Kane and Joe Heinrich -- and "The Designer's Guide to VHDL" by Peter J. Ashenden --------------------------------------------------------------------- library ieee; use ieee.std_logic_1164.all; use work.mlite_pack.all; entity control is port(opcode : in std_logic_vector(31 downto 0); intr_signal : in std_logic; rs_index : out std_logic_vector(5 downto 0); rt_index : out std_logic_vector(5 downto 0); rd_index : out std_logic_vector(5 downto 0); imm_out : out std_logic_vector(15 downto 0); alu_func : out alu_function_type; shift_func : out shift_function_type; mult_func : out mult_function_type; branch_func : out branch_function_type; a_source_out : out a_source_type; b_source_out : out b_source_type; c_source_out : out c_source_type; pc_source_out: out pc_source_type; mem_source_out:out mem_source_type; exception_out: out std_logic); end; --entity control architecture logic of control is begin control_proc: process(opcode, intr_signal) variable op, func : std_logic_vector(5 downto 0); variable rs, rt, rd : std_logic_vector(5 downto 0); variable rtx : std_logic_vector(4 downto 0); variable imm : std_logic_vector(15 downto 0); variable alu_function : alu_function_type; variable shift_function : shift_function_type; variable mult_function : mult_function_type; variable a_source : a_source_type; variable b_source : b_source_type; variable c_source : c_source_type; variable pc_source : pc_source_type; variable branch_function: branch_function_type; variable mem_source : mem_source_type; variable is_syscall : std_logic; begin alu_function := ALU_NOTHING; shift_function := SHIFT_NOTHING; mult_function := MULT_NOTHING; a_source := A_FROM_REG_SOURCE; b_source := B_FROM_REG_TARGET; c_source := C_FROM_NULL; pc_source := FROM_INC4; branch_function := BRANCH_EQ; mem_source := MEM_FETCH; op := opcode(31 downto 26); rs := '0' & opcode(25 downto 21); rt := '0' & opcode(20 downto 16); rtx := opcode(20 downto 16); rd := '0' & opcode(15 downto 11); func := opcode(5 downto 0); imm := opcode(15 downto 0); is_syscall := '0'; case op is when "000000" => --SPECIAL case func is when "000000" => --SLL r[rd]=r[rt]<<re; a_source := A_FROM_IMM10_6; c_source := C_FROM_SHIFT; shift_function := SHIFT_LEFT_UNSIGNED; when "000010" => --SRL r[rd]=u[rt]>>re; a_source := A_FROM_IMM10_6; c_source := C_FROM_shift; shift_function := SHIFT_RIGHT_UNSIGNED; when "000011" => --SRA r[rd]=r[rt]>>re; a_source := A_FROM_IMM10_6; c_source := C_FROM_SHIFT; shift_function := SHIFT_RIGHT_SIGNED; when "000100" => --SLLV r[rd]=r[rt]<<r[rs]; c_source := C_FROM_SHIFT; shift_function := SHIFT_LEFT_UNSIGNED; when "000110" => --SRLV r[rd]=u[rt]>>r[rs]; c_source := C_FROM_SHIFT; shift_function := SHIFT_RIGHT_UNSIGNED; when "000111" => --SRAV r[rd]=r[rt]>>r[rs]; c_source := C_FROM_SHIFT; shift_function := SHIFT_RIGHT_SIGNED; when "001000" => --JR s->pc_next=r[rs]; pc_source := FROM_BRANCH; alu_function := ALU_ADD; branch_function := BRANCH_YES; when "001001" => --JALR r[rd]=s->pc_next; s->pc_next=r[rs]; c_source := C_FROM_PC_PLUS4; pc_source := FROM_BRANCH; alu_function := ALU_ADD; branch_function := BRANCH_YES; --when "001010" => --MOVZ if(!r[rt]) r[rd]=r[rs]; /*IV*/ --when "001011" => --MOVN if(r[rt]) r[rd]=r[rs]; /*IV*/ when "001100" => --SYSCALL is_syscall := '1'; when "001101" => --BREAK s->wakeup=1; is_syscall := '1'; --when "001111" => --SYNC s->wakeup=1; when "010000" => --MFHI r[rd]=s->hi; c_source := C_FROM_MULT; mult_function := MULT_READ_HI; when "010001" => --MTHI s->hi=r[rs]; mult_function := MULT_WRITE_HI; when "010010" => --MFLO r[rd]=s->lo; c_source := C_FROM_MULT; mult_function := MULT_READ_LO; when "010011" => --MTLO s->lo=r[rs]; mult_function := MULT_WRITE_LO; when "011000" => --MULT s->lo=r[rs]*r[rt]; s->hi=0; mult_function := MULT_SIGNED_MULT; when "011001" => --MULTU s->lo=r[rs]*r[rt]; s->hi=0; mult_function := MULT_MULT; when "011010" => --DIV s->lo=r[rs]/r[rt]; s->hi=r[rs]%r[rt]; mult_function := MULT_SIGNED_DIVIDE; when "011011" => --DIVU s->lo=r[rs]/r[rt]; s->hi=r[rs]%r[rt]; mult_function := MULT_DIVIDE; when "100000" => --ADD r[rd]=r[rs]+r[rt]; c_source := C_FROM_ALU; alu_function := ALU_ADD; when "100001" => --ADDU r[rd]=r[rs]+r[rt]; c_source := C_FROM_ALU; alu_function := ALU_ADD; when "100010" => --SUB r[rd]=r[rs]-r[rt]; c_source := C_FROM_ALU; alu_function := ALU_SUBTRACT; when "100011" => --SUBU r[rd]=r[rs]-r[rt]; c_source := C_FROM_ALU; alu_function := ALU_SUBTRACT; when "100100" => --AND r[rd]=r[rs]&r[rt]; c_source := C_FROM_ALU; alu_function := ALU_AND; when "100101" => --OR r[rd]=r[rs]|r[rt]; c_source := C_FROM_ALU; alu_function := ALU_OR; when "100110" => --XOR r[rd]=r[rs]^r[rt]; c_source := C_FROM_ALU; alu_function := ALU_XOR; when "100111" => --NOR r[rd]=~(r[rs]|r[rt]); c_source := C_FROM_ALU; alu_function := ALU_NOR; when "101010" => --SLT r[rd]=r[rs]<r[rt]; c_source := C_FROM_ALU; alu_function := ALU_LESS_THAN_SIGNED; when "101011" => --SLTU r[rd]=u[rs]<u[rt]; c_source := C_FROM_ALU; alu_function := ALU_LESS_THAN; when "101101" => --DADDU r[rd]=r[rs]+u[rt]; c_source := C_FROM_ALU; alu_function := ALU_ADD; --when "110001" => --TGEU --when "110010" => --TLT --when "110011" => --TLTU --when "110100" => --TEQ --when "110110" => --TNE when others => end case; when "000001" => --REGIMM rt := "000000"; rd := "011111"; a_source := A_FROM_PC; b_source := B_FROM_IMMX4; alu_function := ALU_ADD; pc_source := FROM_BRANCH; branch_function := BRANCH_GTZ; --if(test) pc=pc+imm*4 case rtx is when "10000" => --BLTZAL r[31]=s->pc_next; branch=r[rs]<0; c_source := C_FROM_PC_PLUS4; branch_function := BRANCH_LTZ; when "00000" => --BLTZ branch=r[rs]<0; branch_function := BRANCH_LTZ; when "10001" => --BGEZAL r[31]=s->pc_next; branch=r[rs]>=0; c_source := C_FROM_PC_PLUS4; branch_function := BRANCH_GEZ; when "00001" => --BGEZ branch=r[rs]>=0; branch_function := BRANCH_GEZ; --when "10010" => --BLTZALL r[31]=s->pc_next; lbranch=r[rs]<0; --when "00010" => --BLTZL lbranch=r[rs]<0; --when "10011" => --BGEZALL r[31]=s->pc_next; lbranch=r[rs]>=0; --when "00011" => --BGEZL lbranch=r[rs]>=0; when others => end case; when "000011" => --JAL r[31]=s->pc_next; s->pc_next=(s->pc&0xf0000000)|target; c_source := C_FROM_PC_PLUS4; rd := "011111"; pc_source := FROM_OPCODE25_0; when "000010" => --J s->pc_next=(s->pc&0xf0000000)|target; pc_source := FROM_OPCODE25_0; when "000100" => --BEQ branch=r[rs]==r[rt]; a_source := A_FROM_PC; b_source := B_FROM_IMMX4; alu_function := ALU_ADD; pc_source := FROM_BRANCH; branch_function := BRANCH_EQ; when "000101" => --BNE branch=r[rs]!=r[rt]; a_source := A_FROM_PC; b_source := B_FROM_IMMX4; alu_function := ALU_ADD; pc_source := FROM_BRANCH; branch_function := BRANCH_NE; when "000110" => --BLEZ branch=r[rs]<=0; a_source := A_FROM_PC; b_source := b_FROM_IMMX4; alu_function := ALU_ADD; pc_source := FROM_BRANCH; branch_function := BRANCH_LEZ; when "000111" => --BGTZ branch=r[rs]>0; a_source := A_FROM_PC; b_source := B_FROM_IMMX4; alu_function := ALU_ADD; pc_source := FROM_BRANCH; branch_function := BRANCH_GTZ; when "001000" => --ADDI r[rt]=r[rs]+(short)imm; b_source := B_FROM_SIGNED_IMM; c_source := C_FROM_ALU; rd := rt; alu_function := ALU_ADD; when "001001" => --ADDIU u[rt]=u[rs]+(short)imm; b_source := B_FROM_SIGNED_IMM; c_source := C_FROM_ALU; rd := rt; alu_function := ALU_ADD; when "001010" => --SLTI r[rt]=r[rs]<(short)imm; b_source := B_FROM_SIGNED_IMM; c_source := C_FROM_ALU; rd := rt; alu_function := ALU_LESS_THAN_SIGNED; when "001011" => --SLTIU u[rt]=u[rs]<(unsigned long)(short)imm; b_source := B_FROM_SIGNED_IMM; c_source := C_FROM_ALU; rd := rt; alu_function := ALU_LESS_THAN; when "001100" => --ANDI r[rt]=r[rs]&imm; b_source := B_FROM_IMM; c_source := C_FROM_ALU; rd := rt; alu_function := ALU_AND; when "001101" => --ORI r[rt]=r[rs]|imm; b_source := B_FROM_IMM; c_source := C_FROM_ALU; rd := rt; alu_function := ALU_OR; when "001110" => --XORI r[rt]=r[rs]^imm; b_source := B_FROM_IMM; c_source := C_FROM_ALU; rd := rt; alu_function := ALU_XOR; when "001111" => --LUI r[rt]=(imm<<16); c_source := C_FROM_IMM_SHIFT16; rd := rt; when "010000" => --COP0 alu_function := ALU_OR; c_source := C_FROM_ALU; if opcode(23) = '0' then --move from CP0 rs := '1' & opcode(15 downto 11); rt := "000000"; rd := '0' & opcode(20 downto 16); else --move to CP0 rs := "000000"; rd(5) := '1'; pc_source := FROM_BRANCH; --delay possible interrupt branch_function := BRANCH_NO; end if; --when "010001" => --COP1 --when "010010" => --COP2 --when "010011" => --COP3 --when "010100" => --BEQL lbranch=r[rs]==r[rt]; --when "010101" => --BNEL lbranch=r[rs]!=r[rt]; --when "010110" => --BLEZL lbranch=r[rs]<=0; --when "010111" => --BGTZL lbranch=r[rs]>0; when "100000" => --LB r[rt]=*(signed char*)ptr; a_source := A_FROM_REG_SOURCE; b_source := B_FROM_SIGNED_IMM; alu_function := ALU_ADD; rd := rt; c_source := C_FROM_MEMORY; mem_source := MEM_READ8S; --address=(short)imm+r[rs]; when "100001" => --LH r[rt]=*(signed short*)ptr; a_source := A_FROM_REG_SOURCE; b_source := B_FROM_SIGNED_IMM; alu_function := ALU_ADD; rd := rt; c_source := C_FROM_MEMORY; mem_source := MEM_READ16S; --address=(short)imm+r[rs]; when "100010" => --LWL //Not Implemented a_source := A_FROM_REG_SOURCE; b_source := B_FROM_SIGNED_IMM; alu_function := ALU_ADD; rd := rt; c_source := C_FROM_MEMORY; mem_source := MEM_READ32; when "100011" => --LW r[rt]=*(long*)ptr; a_source := A_FROM_REG_SOURCE; b_source := B_FROM_SIGNED_IMM; alu_function := ALU_ADD; rd := rt; c_source := C_FROM_MEMORY; mem_source := MEM_READ32; when "100100" => --LBU r[rt]=*(unsigned char*)ptr; a_source := A_FROM_REG_SOURCE; b_source := B_FROM_SIGNED_IMM; alu_function := ALU_ADD; rd := rt; c_source := C_FROM_MEMORY; mem_source := MEM_READ8; --address=(short)imm+r[rs]; when "100101" => --LHU r[rt]=*(unsigned short*)ptr; a_source := A_FROM_REG_SOURCE; b_source := B_FROM_SIGNED_IMM; alu_function := ALU_ADD; rd := rt; c_source := C_FROM_MEMORY; mem_source := MEM_READ16; --address=(short)imm+r[rs]; --when "100110" => --LWR //Not Implemented when "101000" => --SB *(char*)ptr=(char)r[rt]; a_source := A_FROM_REG_SOURCE; b_source := B_FROM_SIGNED_IMM; alu_function := ALU_ADD; mem_source := MEM_WRITE8; --address=(short)imm+r[rs]; when "101001" => --SH *(short*)ptr=(short)r[rt]; a_source := A_FROM_REG_SOURCE; b_source := B_FROM_SIGNED_IMM; alu_function := ALU_ADD; mem_source := MEM_WRITE16; when "101010" => --SWL //Not Implemented a_source := A_FROM_REG_SOURCE; b_source := B_FROM_SIGNED_IMM; alu_function := ALU_ADD; mem_source := MEM_WRITE32; --address=(short)imm+r[rs]; when "101011" => --SW *(long*)ptr=r[rt]; a_source := A_FROM_REG_SOURCE; b_source := B_FROM_SIGNED_IMM; alu_function := ALU_ADD; mem_source := MEM_WRITE32; --address=(short)imm+r[rs]; --when "101110" => --SWR //Not Implemented --when "101111" => --CACHE --when "110000" => --LL r[rt]=*(long*)ptr; --when "110001" => --LWC1 --when "110010" => --LWC2 --when "110011" => --LWC3 --when "110101" => --LDC1 --when "110110" => --LDC2 --when "110111" => --LDC3 --when "111000" => --SC *(long*)ptr=r[rt]; r[rt]=1; --when "111001" => --SWC1 --when "111010" => --SWC2 --when "111011" => --SWC3 --when "111101" => --SDC1 --when "111110" => --SDC2 --when "111111" => --SDC3 when others => end case; if c_source = C_FROM_NULL then rd := "000000"; end if; if intr_signal = '1' or is_syscall = '1' then rs := "111111"; --interrupt vector rt := "000000"; rd := "101110"; --save PC in EPC alu_function := ALU_OR; shift_function := SHIFT_NOTHING; mult_function := MULT_NOTHING; branch_function := BRANCH_YES; a_source := A_FROM_REG_SOURCE; b_source := B_FROM_REG_TARGET; c_source := C_FROM_PC; pc_source := FROM_LBRANCH; mem_source := MEM_FETCH; exception_out <= '1'; else exception_out <= '0'; end if; rs_index <= rs; rt_index <= rt; rd_index <= rd; imm_out <= imm; alu_func <= alu_function; shift_func <= shift_function; mult_func <= mult_function; branch_func <= branch_function; a_source_out <= a_source; b_source_out <= b_source; c_source_out <= c_source; pc_source_out <= pc_source; mem_source_out <= mem_source; end process; end; --logic
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