pm_fetch_dec.vhd

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signal nret_st0       : std_logic := '0';
signal ret_st1        : std_logic := '0';
signal ret_st2        : std_logic := '0';
signal ret_st3        : std_logic := '0';

signal nreti_st0      : std_logic := '0';
signal reti_st1       : std_logic := '0';
signal reti_st2       : std_logic := '0';
signal reti_st3       : std_logic := '0';

signal brxx_st        : std_logic := '0';  -- BRANCHES

signal adiw_st        : std_logic := '0';
signal sbiw_st        : std_logic := '0';

signal nskip_inst_st0 : std_logic := '0';
signal skip_inst_st1  : std_logic := '0';
signal skip_inst_st2  : std_logic := '0';  -- ALL SKIP INSTRUCTIONS SBRS/SBRC/SBIS/SBIC/CPSE 

signal skip_inst_start  : std_logic := '0';

signal nlpm_st0       : std_logic := '0';
signal lpm_st1        : std_logic := '0';
signal lpm_st2        : std_logic := '0';

signal nelpm_st0      : std_logic := '0';
signal elpm_st1       : std_logic := '0';
signal elpm_st2       : std_logic := '0';

signal nsts_st0       : std_logic := '0';
signal sts_st1        : std_logic := '0';
signal sts_st2        : std_logic := '0';

signal nlds_st0       : std_logic := '0';
signal lds_st1        : std_logic := '0';
signal lds_st2        : std_logic := '0';

signal st_st          : std_logic := '0';
signal ld_st          : std_logic := '0';

signal sbi_st         : std_logic := '0';
signal cbi_st         : std_logic := '0';

signal push_st        : std_logic := '0';
signal pop_st	      : std_logic := '0';

-- INTERNAL STATE MACHINES
signal nop_insert_st  : std_logic := '0';
signal cpu_busy       : std_logic :='0';

-- INTERNAL COPIES OF OUTPUTS
signal pc_int              : std_logic_vector (15 downto 0):=(others =>'0');
signal adr_int             : std_logic_vector (5 downto 0):=(others =>'0');
signal iore_int 		   : std_logic := '0';
signal iowe_int            : std_logic := '0';
signal ramadr_int          : std_logic_vector (15 downto 0):=(others =>'0');
signal ramre_int           : std_logic := '0';
signal ramwe_int           : std_logic := '0';
signal dbusout_int         : std_logic_vector (7 downto 0):=(others =>'0');

-- COMMAND REGISTER
signal instruction_reg      : std_logic_vector (15 downto 0):=(others =>'0'); -- OUTPUT OF THE INSTRUCTION REGISTER
signal instruction_code_reg : std_logic_vector (15 downto 0):=(others =>'0'); -- OUTPUT OF THE INSTRUCTION REGISTER WITH NOP INSERTION
signal instruction_reg_ena  : std_logic := '0';                               -- CLOCK ENABLE


-- IRQ INTERNAL LOGIC
signal irq_int : std_logic;
signal irq_vector_adr : std_logic_vector(15 downto 0):=(others =>'0');
signal irq_pr_encoder : std_logic_vector(6 downto 0):=(others =>'0');

-- INTERRUPT RELATING REGISTERS
signal pc_for_interrupt : std_logic_vector(15 downto 0):=(others =>'0'); 

-- DATA EXTRACTOR SIGNALS
signal dex_dat8_immed  : std_logic_vector (7 downto 0):=(others =>'0');  -- IMMEDIATE CONSTANT (DATA) -> ANDI,ORI,SUBI,SBCI,CPI,LDI
signal dex_dat6_immed  : std_logic_vector (5 downto 0):=(others =>'0');  -- IMMEDIATE CONSTANT (DATA) -> ADIW,SBIW
signal dex_adr12mem_s  : std_logic_vector (11 downto 0):=(others =>'0'); -- RELATIVE ADDRESS (SIGNED) -> RCALL,RJMP
signal dex_adr6port    : std_logic_vector (5 downto 0):=(others =>'0');  -- I/O PORT ADDRESS -> IN,OUT
signal dex_adr5port    : std_logic_vector (4 downto 0):=(others =>'0');  -- I/O PORT ADDRESS -> CBI,SBI,SBIC,SBIS
signal dex_adr_disp    : std_logic_vector (5 downto 0):=(others =>'0');  -- DISPLACEMENT FO ADDDRESS -> STD,LDD
signal dex_condition   : std_logic_vector (2 downto 0):=(others =>'0');  -- CONDITION -> BRBC,BRBS
signal dex_bitnum_sreg : std_logic_vector (2 downto 0):=(others =>'0');  -- NUMBER OF BIT IN SREG -> BCLR,BSET
signal dex_adrreg_r    : std_logic_vector (4 downto 0):=(others =>'0');  -- SOURCE REGISTER ADDRESS -> .......
signal dex_adrreg_d    : std_logic_vector (4 downto 0):=(others =>'0');  -- DESTINATION REGISTER ADDRESS -> ......
signal dex_bitop_bitnum : std_logic_vector(2 downto 0):=(others =>'0');  -- NUMBER OF BIT FOR BIT ORIENTEDE OPERATION -> BST/BLD+SBI/CBI+SBIC/SBIS+SBRC/SBRS !! CHECKED
signal dex_brxx_offset : std_logic_vector (6 downto 0):=(others =>'0');  -- RELATIVE ADDRESS (SIGNED) -> BRBC,BRBS !! CHECKED
signal dex_adiw_sbiw_reg_adr  : std_logic_vector (1 downto 0):=(others =>'0');  -- ADDRESS OF THE LOW REGISTER FOR ADIW/SBIW INSTRUCTIONS

signal dex_adrreg_d_latched : std_logic_vector (4 downto 0):=(others =>'0');   --  STORE ADDRESS OF DESTINATION REGISTER FOR LDS/STS/POP INSTRUCTIONS
signal gp_reg_tmp           : std_logic_vector (7 downto 0):=(others =>'0');   --  STORE DATA FROM THE REGISTERS FOR STS,ST INSTRUCTIONS
signal cbi_sbi_io_adr_tmp   : std_logic_vector (4 downto 0):=(others =>'0');   --  STORE ADDRESS OF I/O PORT FOR CBI/SBI INSTRUCTION
signal cbi_sbi_bit_num_tmp  : std_logic_vector (2 downto 0):=(others =>'0');   --  STORE ADDRESS OF I/O PORT FOR CBI/SBI INSTRUCTION

-- INSTRUCTIONS DECODER SIGNALS

signal idc_adc     : std_logic; -- INSTRUCTION ADC
signal idc_add     : std_logic; -- INSTRUCTION ADD
signal idc_adiw    : std_logic; -- INSTRUCTION ADIW
signal idc_and     : std_logic; -- INSTRUCTION AND
signal idc_andi    : std_logic; -- INSTRUCTION ANDI
signal idc_asr     : std_logic; -- INSTRUCTION ASR

signal idc_bclr    : std_logic; -- INSTRUCTION BCLR
signal idc_bld     : std_logic; -- INSTRUCTION BLD
signal idc_brbc    : std_logic; -- INSTRUCTION BRBC
signal idc_brbs    : std_logic; -- INSTRUCTION BRBS
signal idc_bset    : std_logic; -- INSTRUCTION BSET
signal idc_bst     : std_logic; -- INSTRUCTION BST

signal idc_call    : std_logic; -- INSTRUCTION CALL
signal idc_cbi     : std_logic; -- INSTRUCTION CBI
signal idc_com     : std_logic; -- INSTRUCTION COM
signal idc_cp      : std_logic; -- INSTRUCTION CP
signal idc_cpc     : std_logic; -- INSTRUCTION CPC
signal idc_cpi     : std_logic; -- INSTRUCTION CPI
signal idc_cpse    : std_logic; -- INSTRUCTION CPSE

signal idc_dec     : std_logic; -- INSTRUCTION DEC

signal idc_elpm    : std_logic; -- INSTRUCTION ELPM
signal idc_eor     : std_logic; -- INSTRUCTION EOR

signal idc_icall   : std_logic; -- INSTRUCTION ICALL
signal idc_ijmp    : std_logic; -- INSTRUCTION IJMP

signal idc_in      : std_logic; -- INSTRUCTION IN
signal idc_inc     : std_logic; -- INSTRUCTION INC

signal idc_jmp     : std_logic; -- INSTRUCTION JMP

signal idc_ld_x    : std_logic; -- INSTRUCTION LD Rx,X ; LD Rx,X+ ;LD Rx,-X
signal idc_ld_y    : std_logic; -- INSTRUCTION LD Rx,Y ; LD Rx,Y+ ;LD Rx,-Y
signal idc_ldd_y   : std_logic; -- INSTRUCTION LDD Rx,Y+q
signal idc_ld_z    : std_logic; -- INSTRUCTION LD Rx,Z ; LD Rx,Z+ ;LD Rx,-Z
signal idc_ldd_z   : std_logic; -- INSTRUCTION LDD Rx,Z+q

signal idc_ldi     : std_logic; -- INSTRUCTION LDI
signal idc_lds     : std_logic; -- INSTRUCTION LDS
signal idc_lpm     : std_logic; -- INSTRUCTION LPM
signal idc_lsr     : std_logic; -- INSTRUCTION LSR

signal idc_mov     : std_logic; -- INSTRUCTION MOV
signal idc_mul     : std_logic; -- INSTRUCTION MUL

signal idc_neg     : std_logic; -- INSTRUCTION NEG
signal idc_nop     : std_logic; -- INSTRUCTION NOP

signal idc_or      : std_logic; -- INSTRUCTION OR
signal idc_ori     : std_logic; -- INSTRUCTION ORI
signal idc_out     : std_logic; -- INSTRUCTION OUT

signal idc_pop     : std_logic; -- INSTRUCTION POP
signal idc_push    : std_logic; -- INSTRUCTION PUSH

signal idc_rcall   : std_logic; -- INSTRUCTION RCALL
signal idc_ret     : std_logic; -- INSTRUCTION RET
signal idc_reti    : std_logic; -- INSTRUCTION RETI
signal idc_rjmp    : std_logic; -- INSTRUCTION RJMP
signal idc_ror     : std_logic; -- INSTRUCTION ROR

signal idc_sbc     : std_logic; -- INSTRUCTION SBC
signal idc_sbci    : std_logic; -- INSTRUCTION SBCI
signal idc_sbi     : std_logic; -- INSTRUCTION SBI
signal idc_sbic    : std_logic; -- INSTRUCTION SBIC
signal idc_sbis    : std_logic; -- INSTRUCTION SBIS
signal idc_sbiw    : std_logic; -- INSTRUCTION SBIW
signal idc_sbrc    : std_logic; -- INSTRUCTION SBRC
signal idc_sbrs    : std_logic; -- INSTRUCTION SBRS
signal idc_sleep   : std_logic; -- INSTRUCTION SLEEP

signal idc_st_x    : std_logic; -- INSTRUCTION LD X,Rx ; LD X+,Rx ;LD -X,Rx
signal idc_st_y    : std_logic; -- INSTRUCTION LD Y,Rx ; LD Y+,Rx ;LD -Y,Rx
signal idc_std_y   : std_logic; -- INSTRUCTION LDD Y+q,Rx
signal idc_st_z    : std_logic; -- INSTRUCTION LD Z,Rx ; LD Z+,Rx ;LD -Z,Rx
signal idc_std_z   : std_logic; -- INSTRUCTION LDD Z+q,Rx

signal idc_sts     : std_logic; -- INSTRUCTION STS
signal idc_sub     : std_logic; -- INSTRUCTION SUB
signal idc_subi    : std_logic; -- INSTRUCTION SUBI
signal idc_swap    : std_logic; -- INSTRUCTION SWAP

signal idc_wdr     : std_logic; -- INSTRUCTION WDR


-- ADDITIONAL SIGNALS
signal idc_psinc   :  std_logic; -- POST INCREMENT FLAG FOR LD,ST INSTRUCTIONS
signal idc_prdec   :  std_logic; -- PRE DECREMENT  FLAG FOR LD,ST INSTRUCTIONS

-- ##################################################

-- SREG FLAGS WRITE ENABLE SIGNALS

alias sreg_c_wr_en  : std_logic is sreg_fl_wr_en(0);
alias sreg_z_wr_en  : std_logic is sreg_fl_wr_en(1);
alias sreg_n_wr_en  : std_logic is sreg_fl_wr_en(2);
alias sreg_v_wr_en  : std_logic is sreg_fl_wr_en(3);
alias sreg_s_wr_en  : std_logic is sreg_fl_wr_en(4);
alias sreg_h_wr_en  : std_logic is sreg_fl_wr_en(5);
alias sreg_t_wr_en  : std_logic is sreg_fl_wr_en(6);
alias sreg_i_wr_en  : std_logic is sreg_fl_wr_en(7);

signal sreg_bop_wr_en : std_logic_vector (7 downto 0);                

signal sreg_adr_eq  : std_logic;
-- &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

begin


-- INSTRUCTION FETCH
instruction_reg_ena <= '1'; -- FOR TEST

instruction_fetch:process(clk,nrst)
begin
if nrst='0' then                              -- RESET
instruction_reg <= (others => '0');
elsif (clk='1' and clk'event) then            -- CLOCK
if instruction_reg_ena='1' then               -- CLOCK ENABLE
instruction_reg <= inst;
end if;
end if;
end process;

-- TWO WORDS INSTRUCTION DETECTOR (CONNECTED DIRECTLY TO THE INSTRUCTION REGISTER)
two_word_inst <= '1' when 
((instruction_reg(15 downto 9)&instruction_reg(3 downto 1)="1001010111") or    -- CALL
 (instruction_reg(15 downto 9)&instruction_reg(3 downto 1)="1001010110")) or   -- JMP
 (instruction_reg(15 downto 9)&instruction_reg(3 downto 0) = "10010000000") or -- LDS
 (instruction_reg(15 downto 9)&instruction_reg(3 downto 0) = "10010010000")    -- STS
   else '0';  -- TO DETECT CALL/JMP/LDS/STS INSTRUCTIONS FOR SBRS/SBRC/SBIS/SBIC/CPSE

	
	
-- DATA EXTRACTOR (CONNECTED DIRECTLY TO THE INSTRUCTION REGISTER)
dex_dat8_immed <= instruction_reg(11 downto 8) & instruction_reg(3 downto 0);
dex_dat6_immed <= instruction_reg(7 downto 6) & instruction_reg(3 downto 0);
dex_adr12mem_s <= instruction_reg(11 downto 0); 
dex_adr6port <= instruction_reg(10 downto 9) & instruction_reg(3 downto 0);    
dex_adr5port <= instruction_reg(7 downto 3);  
dex_adr_disp <= instruction_reg(13) & instruction_reg(11 downto 10) & instruction_reg(2 downto 0);      
dex_condition <= instruction_reg(2 downto 0);   
dex_bitop_bitnum <= instruction_reg(2 downto 0);      -- NUMBER(POSITION) OF TESTING BIT IN SBRC/SBRS/SBIC/SBIS INSTRUCTION
dex_bitnum_sreg <= instruction_reg(6 downto 4);    
dex_adrreg_r  <=  instruction_reg(9) & instruction_reg(3 downto 0);
dex_adrreg_d  <= instruction_reg(8 downto 4);     
dex_brxx_offset <= instruction_reg(9 downto 3);       -- OFFSET FOR BRBC/BRBS     
dex_adiw_sbiw_reg_adr <= instruction_reg(5 downto 4); -- ADDRESS OF THE LOW REGISTER FOR ADIW/SBIW INSTRUCTIONS
--dex_adrindreg <= instruction_reg(3 downto 2);     

-- LATCH Rd ADDDRESS FOR LDS/STS/POP INSTRUCTIONS
latcht_rd_adr:process(clk,nrst)
begin
if nrst ='0' then
dex_adrreg_d_latched <= (others => '0');
elsif (clk='1' and clk'event) then
if ((idc_ld_x or idc_ld_y or idc_ldd_y or idc_ld_z or idc_ldd_z) or idc_sts or 
	(idc_st_x  or idc_st_y or idc_std_y or idc_st_z or idc_std_z)or idc_lds or 
	idc_pop)='1' then     -- CLOCK ENABLE
dex_adrreg_d_latched <= dex_adrreg_d;
end if;
end if;
end process;
-- +++++++++++++++++++++++++++++++++++++++++++++++++


-- R24:R25/R26:R27/R28:R29/R30:R31 ADIW/SBIW  ADDRESS CONTROL LOGIC
adiw_sbiw_encoder_out <= "11"&dex_adiw_sbiw_reg_adr&'0';

adiw_sbiw_high_reg_adr:process(clk,nrst)
begin
if nrst ='0' then
adiw_sbiw_encoder_mux_out <= (others=>'0'); 
elsif(clk='1' and clk'event) then
adiw_sbiw_encoder_mux_out <= adiw_sbiw_encoder_out +1;
end if;
end process;
	
-- ##########################

-- NOP INSERT STATE MACHINE
instruction_code_reg <= instruction_reg when nop_insert_st='0' else (others => '0');
	
--nop_insertion:process(clk,nrst)
--begin
--if nrst='0' then                       -- RESET
--nop_insert_st <='0';
--elsif (clk='1' and clk'event) then       -- CLOCK
--end if;
--end process;


nop_insert_st <= adiw_st or sbiw_st or cbi_st or sbi_st or rjmp_st or ijmp_st or pop_st or push_st or