control.vhd

Plasma IP Core 你可以利用这个组件在FPGA中设计MIPS结构的CPU

   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_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];
      a_source := A_FROM_PC;
      b_source := B_FROM_IMMX4;
      alu_function := ALU_ADD;
      pc_source := FROM_LBRANCH;
      branch_function := BRANCH_EQ;

   when "010101" =>   --BNEL   lbranch=r[rs]!=r[rt];
      a_source := A_FROM_PC;
      b_source := B_FROM_IMMX4;
      alu_function := ALU_ADD;
      pc_source := FROM_LBRANCH;
      branch_function := BRANCH_NE;

   when "010110" =>   --BLEZL  lbranch=r[rs]<=0;
      a_source := A_FROM_PC;
      b_source := B_FROM_IMMX4;
      alu_function := ALU_ADD;
      pc_source := FROM_LBRANCH;
      branch_function := BRANCH_LEZ;

   when "010111" =>   --BGTZL  lbranch=r[rs]>0;
      a_source := A_FROM_PC;
      b_source := B_FROM_IMMX4;
      alu_function := ALU_ADD;
      pc_source := FROM_LBRANCH;
      branch_function := BRANCH_GTZ;

   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