* Small ZPU now supports interrupts

	* added simulation example demonstrating interrupts

1 files changed, 59 insertions, 24 deletions

diff --git a/zpu/hdl/zpu4/core/zpu_core_small.vhd b/zpu/hdl/zpu4/core/zpu_core_small.vhd
index 9cda01c..03526bd 100644
--- a/zpu/hdl/zpu4/core/zpu_core_small.vhd
+++ b/zpu/hdl/zpu4/core/zpu_core_small.vhd
@@ -81,7 +81,9 @@ State_FetchNext,
 State_AddSP,

 State_ReadIODone,

 State_Decode,

-State_Resync

+State_Resync,

+State_Interrupt

+

 );

 

 type DecodedOpcodeType is

@@ -103,7 +105,8 @@ Decoded_Load,
 Decoded_Not,

 Decoded_Flip,

 Decoded_Store,

-Decoded_PopSP

+Decoded_PopSP,

+Decoded_Interrupt

 );

 

 

@@ -125,11 +128,15 @@ signal memBAddr_stdlogic  : std_logic_vector(AddrBitBRAM_range);
 signal memBWrite_stdlogic : std_logic_vector(memBWrite'range);

 signal memBRead_stdlogic  : std_logic_vector(memBRead'range);

 

--- debug
-subtype index is integer range 0 to 3;
-signal tOpcode_sel : index;
-
-
+subtype index is integer range 0 to 3;

+

+signal tOpcode_sel : index;

+

+

+signal inInterrupt : std_logic;

+

+

+

 begin

 	traceFileGenerate:

    if Generate_Trace generate

@@ -146,8 +153,13 @@ begin
         );

 	end generate;

 

-	--<JK> not used in this design
-	mem_writeMask <= (others => '1');
+

+

+    -- not used in this design

+

+    mem_writeMask <= (others => '1');

+

+

 

 	memAAddr_stdlogic  <= std_logic_vector(memAAddr(AddrBitBRAM_range));

 	memAWrite_stdlogic <= std_logic_vector(memAWrite);

@@ -167,23 +179,31 @@ begin
 	memARead <= unsigned(memARead_stdlogic);

 	memBRead <= unsigned(memBRead_stdlogic);

 

-tOpcode_sel <= to_integer(pc(minAddrBit-1 downto 0));
+

+

+	tOpcode_sel <= to_integer(pc(minAddrBit-1 downto 0));

+

 

 

 	decodeControl:

-	process(memBRead, pc,tOpcode_sel)
+	process(memBRead, pc,tOpcode_sel)

 		variable tOpcode : std_logic_vector(OpCode_Size-1 downto 0);

 	begin

-		--<JK> not worked with synopsys
-		--<JK> tOpcode := std_logic_vector(memBRead((wordBytes-1-to_integer(pc(minAddrBit-1 downto 0))+1)*8-1 downto (wordBytes-1-to_integer(pc(minAddrBit-1 downto 0)))*8));
-		--<JK> use full case
-		case (tOpcode_sel) is
-			when 0 => tOpcode := std_logic_vector(memBRead(31 downto 24));
-			when 1 => tOpcode := std_logic_vector(memBRead(23 downto 16));
-			when 2 => tOpcode := std_logic_vector(memBRead(15 downto 8));
-			when 3 => tOpcode := std_logic_vector(memBRead(7 downto 0));
-			when others => tOpcode := std_logic_vector(memBRead(7 downto 0));
-		end case;
+

+        -- simplify opcode selection a bit so it passes more synthesizers

+        case (tOpcode_sel) is

+

+            when 0 => tOpcode := std_logic_vector(memBRead(31 downto 24));

+

+            when 1 => tOpcode := std_logic_vector(memBRead(23 downto 16));

+

+            when 2 => tOpcode := std_logic_vector(memBRead(15 downto 8));

+

+            when 3 => tOpcode := std_logic_vector(memBRead(7 downto 0));

+

+            when others => tOpcode := std_logic_vector(memBRead(7 downto 0));

+        end case;

+

 		sampledOpcode <= tOpcode;

 

 		if (tOpcode(7 downto 7)=OpCode_Im) then

@@ -246,13 +266,12 @@ tOpcode_sel <= to_integer(pc(minAddrBit-1 downto 0));
 			out_mem_readEnable <= '0';

 			memAWrite <= (others => '0');

 			memBWrite <= (others => '0');

-			-- avoid Latch in synopsys
-			-- mem_writeMask <= (others => '1');
+			inInterrupt <= '0';

 		elsif (clk'event and clk = '1') then

 			memAWriteEnable <= '0';

 			memBWriteEnable <= '0';

 			-- This saves ca. 100 LUT's, by explicitly declaring that the

-			-- memAWrite can be left at whatever value if memAWriteEnable is

+            -- memAWrite can be left at whatever value if memAWriteEnable is

 			-- not set.

 			memAWrite <= (others => DontCareValue);

 			memBWrite <= (others => DontCareValue);

@@ -270,6 +289,9 @@ tOpcode_sel <= to_integer(pc(minAddrBit-1 downto 0));
 			

 			decodedOpcode <= sampledDecodedOpcode;

 			opcode <= sampledOpcode;

+			if interrupt='0' then

+				inInterrupt <= '0'; -- no longer in an interrupt

+			end if;

 

 			case state is

 				when State_Execute =>

@@ -295,6 +317,14 @@ tOpcode_sel <= to_integer(pc(minAddrBit-1 downto 0));
 	

 					idim_flag <= '0';

 					case decodedOpcode is

+						when Decoded_Interrupt =>

+							sp <= sp - 1;

+							memAAddr <= sp - 1;

+							memAWriteEnable <= '1';

+							memAWrite <= (others => DontCareValue);

+							memAWrite(maxAddrBit downto 0) <= pc;

+							pc <= to_unsigned(32, maxAddrBit+1); -- interrupt address

+			  				report "ZPU jumped to interrupt!" severity note;

 						when Decoded_Im =>

 							idim_flag <= '1';

 							memAWriteEnable <= '1';

@@ -422,6 +452,11 @@ tOpcode_sel <= to_integer(pc(minAddrBit-1 downto 0));
 					memBAddr <= sp + 1;

 					state <= State_Decode;

 				when State_Decode =>

+					if interrupt='1' and inInterrupt='0' and idim_flag='0' then

+						-- We got an interrupt, execute interrupt instead of next instruction

+						inInterrupt <= '1';

+						decodedOpcode <= Decoded_Interrupt;

+					end if;

 					-- during the State_Execute cycle we'll be fetching SP+1

 					memAAddr <= sp;

 					memBAddr <= sp + 1;