ELEC40006-P1-CW/LIFOstack.v

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2020-06-11 16:28:00 +00:00
module LIFOstack (Din, clk, en, rst, rw, Dout);
input [15:0] Din; // Data being fed to stack
input clk; // clock signal input
input en; // disable stack when not in use
input rst; // reset pin to clear and reinitialise stack (active high)
input rw; // 0: read, 1: write
output reg [15:0] Dout; // Data being pulled from stack
2020-06-11 16:28:00 +00:00
reg empty; // goes high to indicate SP is at 0
reg full; // goes high to indicate SP is at (slots)
reg [5:0] SP; // Points to slot to save next value to
integer i;
reg [15:0] mem [31:0];
always @ (posedge clk) begin
if (!en); // if not enabled, ignore this cycle
else begin
if (rst) begin // if rst is high, clear memory and reset pointers/outputs
Dout = 16'h0000;
SP = 6'b000000;
empty = 1'b1;
for (i = 0; i < 32; i = i + 1) begin
mem[i] = 16'h0000;
end
end
else begin
if (!full && rw) begin // Write when NOT full & Writing
mem[SP] = Din; // Store data into current slot
SP = SP + 1'b1; // Increment stack pointer to next empty slot
full = (SP == 6'b100000) ? 1 : 0; // Stack is full if SP is (slots)
empty = 1'b0; // Stack is never empty after a push
end
else if (!empty && !rw) begin // Read when NOT empty & reading
SP = SP - 1'b1; // Decrement stack pointer to last filled slot
Dout = mem[SP]; // Output data from last filled slot
mem[SP] = 16'h0000; // Clear slot after setting output
full = 1'b0; // Stack is never full after a pop
empty = (SP == 6'b000000) ? 1 : 0; // Stack is empty if SP is 0
end
end
end
end
endmodule