restore file

verilog/rtl/cells.v

diff --git a/verilog/rtl/cells.v b/verilog/rtl/cells.v
new file mode 100644
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--- /dev/null
+++ b/verilog/rtl/cells.v
@@ -0,0 +1,96 @@
+`define default_netname none
+
+module buffer_cell (
+    input wire in,
+    output wire out
+    );
+    assign out = in;
+endmodule
+
+module and_cell (
+    input wire a,
+    input wire b,
+    output wire out
+    );
+
+    assign out = a & b;
+endmodule
+
+module or_cell (
+    input wire a,
+    input wire b,
+    output wire out
+    );
+
+    assign out = a | b;
+endmodule
+
+module xor_cell (
+    input wire a,
+    input wire b,
+    output wire out
+    );
+
+    assign out = a ^ b;
+endmodule
+
+module nand_cell (
+    input wire a,
+    input wire b,
+    output wire out
+    );
+
+    assign out = !(a&b);
+endmodule
+
+module not_cell (
+    input wire in,
+    output wire out
+    );
+
+    assign out = !in;
+endmodule
+
+module mux_cell (
+    input wire a,
+    input wire b,
+    input wire sel,
+    output wire out
+    );
+
+    assign out = sel ? b : a;
+endmodule
+
+module dff_cell (
+    input wire clk,
+    input wire d,
+    output reg q,
+    output wire notq
+    );
+
+    assign notq = !q;
+    always @(posedge clk)
+        q <= d;
+
+endmodule
+
+module dffsr_cell (
+    input wire clk,
+    input wire d,
+    input wire s,
+    input wire r,
+    output reg q,
+    output wire notq
+    );
+
+    assign notq = !q;
+
+    always @(posedge clk or posedge s or posedge r) begin
+        if (r)
+            q <= '0;
+        else if (s)
+            q <= '1;
+        else
+            q <= d;
+    end
+endmodule