newStep.v

RTL/DEVICES/SDCard.v

@@ -0,0 +1,40 @@
+// femtorv32, a minimalistic RISC-V RV32I core
+//       Bruno Levy, 2020-2021
+//
+// This file: driver for SDCard (does nearly nothing,
+// for now it is just an interface for software bitbanging,
+// see FIRMWARE/LIBFEMTORV32/spi_sd.c)
+//
+
+module SDCard(
+    input wire 	       clk,   // system clock
+    input wire 	       rstrb, // read strobe		
+    input wire 	       wstrb, // write strobe
+    input wire 	       sel,   // select (read/write ignored if low)
+    input wire [31:0]  wdata, // data to be written
+    output wire [31:0] rdata, // read data
+
+    output wire        MOSI,
+    input wire 	       MISO,
+    output wire	       CS_N,
+    output wire        CLK
+);
+   reg [2:0] state; // CS_N,CLK,MOSI
+
+   assign CS_N = state[2];
+   assign CLK  = state[1];
+   assign MOSI = state[0];
+   
+   initial begin
+      state = 3'b100;
+   end
+   
+   assign rdata = (sel ? {31'b0, MISO} : 32'b0);
+   
+   always @(posedge clk) begin
+      if(sel && wstrb) begin
+	 state <= wdata[2:0];
+      end
+   end
+   
+endmodule