From 32388b786d96e16d5264fe541d217ba5ca6b7084 Mon Sep 17 00:00:00 2001
From: Rutherther <rutherther@proton.me>
Date: Sat, 11 Nov 2023 12:56:18 +0100
Subject: [PATCH] feat: add support for loading and saving ram from disk

---
 src/ram.sv                  | 26 +++++++++++++++++++++++---
 testbench/tb_cpu_program.sv | 24 ++++++++++++++++++++----
 2 files changed, 43 insertions(+), 7 deletions(-)

diff --git a/src/ram.sv b/src/ram.sv
index b324184..5fc65c1 100755
--- a/src/ram.sv
+++ b/src/ram.sv
@@ -7,9 +7,14 @@ module ram (
   output [31:0] rd);
 
   reg [31:0]      mask;
-  reg [31:0]      memory[128];
+  reg [31:0]      memory[1023];
 
-  assign rd = memory[a[8:2]]; // word aligned
+  assign rd = memory[a[11:2]]; // word aligned
+
+  parameter        LOAD_FILE = 0;
+  parameter string LOAD_FILE_PATH = "";
+  parameter        WRITE_FILE = 0;
+  parameter string WRITE_FILE_PATH = "";
 
   always_comb begin
     mask = {
@@ -20,8 +25,23 @@ module ram (
             };
   end
 
+  initial
+    if (LOAD_FILE == 1) begin
+      $display("Loading file %s into memory.", LOAD_FILE_PATH);
+      $readmemh(LOAD_FILE_PATH, memory);
+    end
+
+  initial begin
+    if (WRITE_FILE == 1) begin
+      wait (a == {32{1'b1}});
+      #5
+      $display("Writing memory to file %s.", WRITE_FILE_PATH);
+      $writememh(WRITE_FILE_PATH, memory);
+    end
+  end
+
   always_ff @ (posedge clk)
     if(we)
-      memory[a[8:2]] = (rd & ~mask) | (wd & mask);
+      memory[a[11:2]] = (rd & ~mask) | (wd & mask);
 
 endmodule
diff --git a/testbench/tb_cpu_program.sv b/testbench/tb_cpu_program.sv
index 1a42308..ce00ea0 100755
--- a/testbench/tb_cpu_program.sv
+++ b/testbench/tb_cpu_program.sv
@@ -3,7 +3,7 @@ import cpu_types::*;
 module tb_cpu_program();
   reg clk, rst_n;
 
-  wire [31:0] memory_address, memory_write, memory_out;
+  wire [31:0] memory_address, cpu_memory_address, memory_write, memory_out;
   wire [3:0]  memory_write_byte_enable;
   wire        memory_we;
 
@@ -15,6 +15,14 @@ module tb_cpu_program();
   parameter string  CPU_PROGRAM_PATH;
   parameter string  CPU_PROGRAM_NAME;
 
+  parameter         MEMORY_LOAD_FILE = 0;
+  parameter string  MEMORY_LOAD_FILE_PATH = "";
+  parameter         MEMORY_WRITE_FILE = 0;
+  parameter string  MEMORY_WRITE_FILE_PATH = "";
+
+  // assign 0xFF... when ebreak. To save the memory to a file.
+  assign memory_address = ebreak == 1'b1 ? {32{1'b1}} : cpu_memory_address;
+
   cpu uut(
     .clk(clk),
     .rst_n(rst_n),
@@ -22,7 +30,7 @@ module tb_cpu_program();
     .instruction(instruction),
     .pc(pc),
 
-    .memory_address(memory_address),
+    .memory_address(cpu_memory_address),
     .memory_out(memory_out),
     .memory_write(memory_write),
     .memory_byte_enable(memory_write_byte_enable),
@@ -31,7 +39,12 @@ module tb_cpu_program();
     .ebreak(ebreak)
   );
 
-  ram memory_inst(
+  ram #(
+    .LOAD_FILE(MEMORY_LOAD_FILE),
+    .LOAD_FILE_PATH(MEMORY_LOAD_FILE_PATH),
+    .WRITE_FILE(MEMORY_WRITE_FILE),
+    .WRITE_FILE_PATH(MEMORY_WRITE_FILE_PATH)
+  ) memory_inst(
     .clk(clk),
     .a(memory_address),
     .write_byte_enable(memory_write_byte_enable),
@@ -40,12 +53,15 @@ module tb_cpu_program();
     .rd(memory_out)
   );
 
-  file_program_memory #(.FILE_NAME(CPU_PROGRAM_PATH)) prog_mem_inst(
+  file_program_memory #(
+    .FILE_NAME(CPU_PROGRAM_PATH)
+  ) prog_mem_inst(
     .addr(pc[11:0]),
     .instruction(instruction)
   );
 
   always_ff @ (posedge ebreak) begin
+    $display("ebreak!");
     #15 $finish;
   end
 
-- 
2.48.1