data_mem.v

/*
Module	: 256x8-bit data memory (4-Byte blocks)
Author	: Isuru Nawinne
Date    	: 30/05/2020

Description	:

This file presents a primitive data memory module for CO224 Lab 6 - Part 2
This memory allows data to be read and written as 4-Byte blocks
*/
`timescale  1ns/100ps
module data_memory(
	clock,
    reset,
    read,
    write,
    address,
    writedata,
    readdata,
	busywait
);
input				clock;
input           	reset;
input           	read;
input           	write;
input[5:0]      	address;
input[31:0]     	writedata;
output reg [31:0]	readdata;
output reg      	busywait;

//Declare memory array 256x8-bits 
reg [7:0] memory_array [255:0];

initial
	begin 
		$dumpfile("cpu_wavedata.vcd");
		for(i=0;i<256;i++)
			$dumpvars(1,memory_array[i]);

	end
//Detecting an incoming memory access
reg readaccess, writeaccess;
always @(read, write)
begin
	busywait = (read || write)? 1 : 0;
	readaccess = (read && !write)? 1 : 0;
	writeaccess = (!read && write)? 1 : 0;
end

//Reading & writing
always @(posedge clock)
begin
	if(readaccess)
	begin
		readdata[7:0]   = #40 memory_array[{address,2'b00}];
		readdata[15:8]  = #40 memory_array[{address,2'b01}];
		readdata[23:16] = #40 memory_array[{address,2'b10}];
		readdata[31:24] = #40 memory_array[{address,2'b11}];
		busywait = 0;
		readaccess = 0;
	end
	if(writeaccess)
	begin
		memory_array[{address,2'b00}] = #40 writedata[7:0];
		memory_array[{address,2'b01}] = #40 writedata[15:8];
		memory_array[{address,2'b10}] = #40 writedata[23:16];
		memory_array[{address,2'b11}] = #40 writedata[31:24];
		busywait = 0;
		writeaccess = 0;
	end
end

//Reset memory
integer i;
always @(posedge reset)
begin
    if (reset)
    begin
        for (i=0;i<256; i=i+1)
            memory_array[i] = 0;
        
        busywait = 0;
		readaccess = 0;
		writeaccess = 0;
    end
end

endmodule