Fixed video, kbd and buzzer

cpu/toplevel/tb_ram.sv

@@ -0,0 +1,41 @@
+//--------------------------------------------------------------
+// Implements RAM Model for simulation
+// Loads in a file "ram.hexdump" before execution.
+//--------------------------------------------------------------
+module ram (Address, Data, CS, WE, OE);
+
+// Set this to 1 if you want debug printout on each RAM access
+int debug = 0;
+
+input [15:0] Address;
+inout [7:0] Data;
+input CS, WE, OE;
+
+reg [7:0] Mem [0:1<<16];
+
+// Return data at the specified memory address; return 0x76 for non-initialized memory
+assign Data = (!CS && !OE) ? (Mem[Address]===8'hxx) ? 8'h76 : Mem[Address] : {8{1'bz}};
+
+// Read the initial content of the RAM memory from a file
+initial begin : init
+    // Read the CPU code (address 0) to simulate
+    $readmemh("ram.hexdump", Mem, 0);
+end : init
+
+always @(!CS && !OE) begin
+    if (debug)
+        $strobe("[ram] RD A=%H, D=%H", Address, Data);
+end
+
+always @(CS or WE)
+    if (!CS && !WE) begin
+        if (debug)
+            $strobe("[ram] WR A=%H, D=%H", Address, Data);
+        Mem[Address] = Data;
+    end
+
+always @(WE or OE)
+    if (!WE && !OE)
+        $display("[ram] error: OE and WE both active!");
+
+endmodule