Start reworking fpga impl

1 files changed, 32 insertions, 0 deletions

diff --git a/atk16_fpga/mmodel_sram.v b/atk16_fpga/mmodel_sram.v
new file mode 100644
index 0000000..c0e5a0b
--- /dev/null
+++ b/atk16_fpga/mmodel_sram.v
@@ -0,0 +1,32 @@
+`default_nettype none `timescale 1 ns / 100 ps
+
+// This is a memory model of the SRAM chip on the iCE40HX8K-EVB.
+// Relevant specs:
+// - 256Kx16 capacity
+// - 18-bit address bus, 16-bit data bus
+// - 10 ns read or write cycle time
+// - 3 ns output hold from address change
+module mmodel_sram (
+    input wire cs_n,
+    input wire wr_n,
+    input wire rd_n,
+    input wire [17:0] addr,
+    input wire [15:0] data_in,
+    output reg [15:0] data_out
+);
+    reg [15:0] mem[0:262143];  // 256K x 16 memory
+
+    always @(cs_n or wr_n or rd_n or addr or data_in) begin
+        if (cs_n == 1'b1) begin
+            data_out <= #3 16'hx;
+        end
+        if (cs_n == 1'b0 && wr_n == 1'b0) begin
+            mem[addr] <= #3 16'hx;
+            mem[addr] <= #7 data_in;
+        end
+        if (cs_n == 1'b0 && rd_n == 1'b0) begin
+            data_out <= #3 16'hx;
+            data_out <= #7 mem[addr];
+        end
+    end
+endmodule