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RTL/ALU.sv

@@ -1,46 +1,32 @@
 // Module Name: ALU
 // Project Name: CSE141L
-//
-// Additional Comments:
-//   combinational (unclocked) ALU
+// Description: combinational (unclocked) ALU
 
-// includes package "Definitions"
-// be sure to adjust "Definitions" to match your final set of ALU opcodes
 import Definitions::*;
 
 module ALU #(parameter W=8)(
-  input        [W-1:0]   InputA,       // data inputs
-                         InputB,
-  input        op_mne    OP,           // ALU opcode, part of microcode
-  input                  SC_in,        // shift or carry in
+	input [W-1:0] A, B, // data inputs
+	input op_mne ALU_OP, // ALU opcode, part of microcode
 	output logic [W-1:0] Out, // data output
-  output logic           Zero,         // output = zero flag    !(Out)
-                         Parity,       // outparity flag        ^(Out)
-                         Odd,          // output odd flag        (Out[0])
-						 SC_out        // shift or carry out
-  // you may provide additional status flags, if desired
-  // comment out or delete any you don't need
+	output logic Zero // zero flag
 );
 
-always_comb begin
-// No Op = default
-// add desired ALU ops, delete or comment out any you don't need
-  Out = 8'b0;				                        // don't need NOOP? Out = 8'bx
-  SC_out = 1'b0;		 							// 	 will flag any illegal opcodes
-  case(OP)
-    ADD : {SC_out,Out} = InputA + InputB + SC_in;   // unsigned add with carry-in and carry-out
-    LSH : {SC_out,Out} = {InputA[7:0],SC_in};       // shift left, fill in with SC_in, fill SC_out with InputA[7]
-// for logical left shift, tie SC_in = 0
-    RSH : {Out,SC_out} = {SC_in, InputA[7:0]};      // shift right
-    XOR : Out = InputA ^ InputB;                    // bitwise exclusive OR
-    AND : Out = InputA & InputB;                    // bitwise AND
-    SUB : {SC_out,Out} = InputA + (~InputB) + 1;	// InputA - InputB;
-    CLR : {SC_out,Out} = 'b0;
+	always_comb begin
+		case(ALU_OP)
+			NOP: Out = A; // pass A to out
+			INC: Out = A + 1; // imcrement A by 1
+			DEC: Out = A - 1; // decrement A by 1
+			CLB: Out = {1'b0, A[6:0]}; // set MSB of A to 0
+			ADD: Out = A + B; // add A to B
+			SUB: Out = A - B; // subtract B from A
+			ORR: Out = A | B; // bitwise OR between A and B
+			AND: Out = A & B; // bitwise AND between A and B
+			LSH: Out = A << B; // shift A by B bits
+			RXOR_7: Out = ^(A[6:0]); // perform reduction XOR of lower 7 bits of A
+			RXOR_8: Out = ^(A[7:0]); // perform reduction XOR of lower 8 bits of A
+			XOR: Out = A ^ B; // bitwise XOR between A and B
+			default: Out = 'bx; // flag illegal ALU_OP values
 		endcase
-end
-
-assign Zero   = ~|Out;                  // reduction NOR	 Zero = !Out; 
-assign Parity = ^Out;                   // reduction XOR
-assign Odd    = Out[0];                 // odd/even -- just the value of the LSB
-
+		Zero = Out == 0;
+	end
 endmodule

RTL/Definitions.sv

@@ -1,16 +1,22 @@
-//This file defines the parameters used in the alu
-// CSE141L
-//	Rev. 2022.5.27
-// import package into each module that needs it
-//   packages very useful for declaring global variables
-// need > 8 instructions?
-// typedef enum logic[3:0] and expand the list of enums
+// Module Name: ALU
+// Project Name: CSE141L
+// Description: contains enumerated ALU operations
+
 package Definitions;
 
-// enum names will appear in timing diagram
-// ADD = 3'b000; LSH = 3'b001; etc. 3'b111 is undefined here
-  typedef enum logic[2:0] {
-      ADD, LSH, RSH, XOR,
-      AND, SUB, CLR } op_mne;
+	typedef enum logic[3:0] {
+		NOP, // perform a simple value passthrough
+		INC, // increment by 1
+		DEC, // decrement by 1
+		CLB, // clear leading bit
+		ADD, // addition
+		SUB, // subtraction
+		ORR, // bitwise OR
+		AND, // bitwise AND
+		LSH, // left shift
+		RXOR_7, // reduction XOR with lower 7 bits
+		RXOR_8, // reduction XOR with lower 8 bits
+		XOR // bitwise XOR
+		} op_mne;
     
 endpackage // definitions

RTL/Immediate_LUT.sv

@@ -1,26 +0,0 @@
-/* CSE141L
-   possible lookup table for PC target
-   leverage a few-bit pointer to a wider number
-   Lookup table acts like a function: here Target = f(Addr);
- in general, Output = f(Input); lots of potential applications 
-*/
-module Immediate_LUT #(PC_width = 10)(
-  input               [ 2:0] addr,
-  output logic[PC_width-1:0] datOut
-  );
-
-always_comb begin
-  datOut = 'h001;	          // default to 1 (or PC+1 for relative)
-  case(addr)		   
-	2'b00:   datOut = 'hfc;   // -4, i.e., move back 16 lines of machine code
-	2'b01:	 datOut = 'h03;
-	2'b10:	 datOut = 'h07;
-  endcase
-end
-
-endmodule
-
-
-			 // 3fc = 1111111100 -4
-			 // PC    0000001000  8
-			 //       0000000100  4  

RTL/InstFetch.sv

@@ -1,37 +1,24 @@
-// Design Name:    basic_proc
-// Module Name:    InstFetch 
+// Module Name: ALU
 // Project Name: CSE141L
 // Description: instruction fetch (pgm ctr) for processor
-//
-// Revision:  2021.11.27
-// Suggested ProgCtr width 10 t0 12 bits
-module InstFetch #(parameter T=10)(	  // PC width -- up to 32, if you like
-  input                Reset,		  // reset, init, etc. -- force PC to 0 
-                       Start,		  // begin next program in series (request issued by test bench)
-                       Clk,			  // PC can change on pos. edges only
-                       BranchAbs,	  // jump conditionally to Target value	   
-                       BranchRelEn,	  // jump conditionally to Target + PC
-                       ALU_flag,	  // flag from ALU, e.g. Zero, Carry, Overflow, Negative (from ARM)
-  input        [T-1:0] Target,	      // jump ... "how high?"
-  output logic [T-1:0] ProgCtr        // the program counter register itself
-  );
 
-// you may wish to use either absolute or relative branching
-//   you may use both, but you will need appropriate control bits
-// branch/jump is how we handle gosub and return to main
-// program counter can clear to 0, increment, or branch
-// for unconditional branching, "ALU_flag" input should be driven by 1
-  always_ff @(posedge Clk)	           // or just always; always_ff is a linting construct
-	if(Reset)
-	  ProgCtr <= 0;				       // for first program; want different value for 2nd or 3rd
-	else if(Start)					   // hold while start asserted; commence when released
-	  ProgCtr <= 0;                    //or <= ProgCtr;   holds at starting value
-	else if(BranchAbs && ALU_flag      // unconditional absolute jump
-	  ProgCtr <= Target;			   //   how would you make it conditional and/or relative?
-	else if(BranchRelEn && ALU_flag)   // conditional relative jump
-	  ProgCtr <= Target + ProgCtr;	   //   how would you make it unconditional and/or absolute
-	else
-	  ProgCtr <= ProgCtr+'b1; 	       // default increment (no need for ARM/MIPS +4 -- why?)
+module InstFetch #(parameter T=10, parameter W=8)(	  // T is PC address size, W is the jump target pointer width, which is less
+	input logic Clk, Reset, // clock, reset
+	input logic BranchEZ, BranchNZ, BranchAlways, Zero, // branch control signals zero from alu signals; brnahc signals will be one hot encoding
+	input logic done // Done flag to indicate if the PC should increment at all
+	input logic [W-1:0] Target, // jump target pointer
+	output logic [T-1:0] ProgCtr_p4 // value of pc+4 for use in JAL instruction itself
+);
+
+	logic [T-1:0] PC;
+
+	always_ff @(posedge Clk) begin
+		if(Reset) PC <= 0; // if reset, set PC to 0
+		else if (BranchAlways) PC <= Target; // if unconditional branch, assign PC to target
+		else if (BranchEZ && Zero) PC <= Target; // if branch on zero and zero is true, then assign PC to target
+		else if (BranchNZ && !Zero) PC <= Target; // if branch on non zero and zero is false, then assign PC to parget
+		else if (!done) PC <= PC + 'b1; // if not a branch but CPU is not done, then 
+		else PC <= PC;
+	end
 
 endmodule
-

RTL/RegFile.sv

@@ -1,46 +1,37 @@
-// Create Date:    2019.01.25
-// Design Name:    CSE141L
-// Module Name:    reg_file 
-// Revision:       2022.05.04
-// Additional Comments: 	allows preloading with user constants
-// This version is fully synthesizable and highly recommended.
+// Module Name: ALU
+// Project Name: CSE141L
+// Description: register file
 
-/* parameters are compile time directives 
-       this can be an any-width, any-depth reg_file: just override the params!
-*/
 module RegFile #(parameter W=8, D=4)(		 // W = data path width (leave at 8); D = address pointer width
-  input                Clk,
-                       Reset,	             // note use of Reset port
-                       WriteEn,
-  input        [D-1:0] RaddrA,				 // address pointers
-                       RaddrB,
-                       Waddr,
-  input        [W-1:0] DataIn,
-  output       [W-1:0] DataOutA,			 // showing two different ways to handle DataOutX, for
-  output logic [W-1:0] DataOutB				 //   pedagogic reasons only
-    );
+	input Clk, Reset, WriteEn,
+	input [D-1:0] RaddrA, RaddrB, Waddr, // read anad write address pointers
+	input [W-1:0] DataIn, // data to be written
+	input Zero_in, Done_in, // since flags are stored in register file, need this as an input
+	output logic [W-1:0] DataOutA, DataOutB, // data to read out
+	output logic Zero_out, Done_out // output of zero and done flags
+);
 
-// W bits wide [W-1:0] and 2**4 registers deep 	 
-logic [W-1:0] Registers[2**D];	             // or just registers[16] if we know D=4 always
+	logic [W-1:0] Registers[2**D]; // 2^D registers of with W
+	logic Zero, Done;
 
-// combinational reads 
-/* can use always_comb in place of assign
-    difference: assign is limited to one line of code, so
-	always_comb is much more versatile     
-*/
-assign      DataOutA = Registers[RaddrA];	 // assign & always_comb do the same thing here 
-always_comb DataOutB = Registers[RaddrB];    // can read from addr 0, just like ARM
+	// combination read
+	assign DataOutA = Registers[RaddrA];
+	assign DataOutB = Registers[RaddrB];
+	assign Zero_out = Zero;
+	assign Done_out = Done;
 
-// sequential (clocked) writes 
-always_ff @ (posedge Clk)
-  if (Reset) begin
-	for(int i=0; i<2**D; i++)
+	// sequential (clocked) writes 
+	always_ff @ (posedge Clk) begin
+		if (Reset) begin // reset all registers to 0 when reset
+			for(int i=0; i<2**D; i++) begin
 				Registers[i] <= 'h0;
-// we can override this universal clear command with desired initialization values
-	Registers[0] <= 'd30;                    // loads 30 (=0x1E) into RegFile address 0
-	Registers[2] <= 'b101;                   // loads 00000101 into RegFile address 2 
 			end
-  else if (WriteEn)	                         // works just like data_memory writes
+		end
+		else if (WriteEn) begin
 			Registers[Waddr] <= DataIn;
+			Zero <= Zero_in;
+			Done <= Done_in;
+		end
+	end
 
 endmodule

firmware/program1.asm

@@ -60,7 +60,6 @@ lfsr_routine: GET r7 // get previous state
 	PUT r7 // put next state to r7
 	GET r14 // load link register
 	JMP r0 // return to function call address
-done: LDI #b10000000 // load the processor flag state needed to halt the program
-	PUT r15 // put and set the done flag to 1 to halt the PC and indicate the program has finished
+done: DNE // flag the CPU as done
 	LDI #d255
 	JMP r0

firmware/program2.asm

@@ -101,7 +101,6 @@ lfsr_routine: GET r7 // get previous state
 	PUT r7 // put next state to r7
 	GET r14 // load link register
 	JMP r0 // return to function call address
-done: LDI #b10000000 // load the processor flag state needed to halt the program
-	PUT r15 // put and set the done flag to 1 to halt the PC and indicate the program has finished
+done: DNE // flag the CPU as done
 	LDI #d255
 	JMP r0

firmware/program3.asm

@@ -109,7 +109,6 @@ lfsr_routine: GET r7 // get previous state
 	PUT r7 // put next state to r7
 	GET r14 // load link register
 	JMP r0 // return to function call address
-done: LDI #b10000000 // load the processor flag state needed to halt the program
-	PUT r15 // put and set the done flag to 1 to halt the PC and indicate the program has finished
+done: DNE // flag the CPU as done
 	LDI #d255
 	JMP r0