Add sd card cs

hw/fpga/addr_decode.sv

@@ -6,8 +6,9 @@ module addr_decode(
     output logic uart_cs,
     output logic irq_cs,
     output logic board_io_cs,
-	output logic mm_cs1,
-	output logic mm_cs2
+    output logic mm_cs1,
+    output logic mm_cs2,
+    output logic sd_cs
 );
 
 assign rom_cs = addr >= 24'h008000 && addr < 24'h010000;
@@ -17,6 +18,7 @@ assign hex_cs = addr >= 24'h007ff0 && addr < 24'h007ff4;
 assign uart_cs = addr >= 24'h007ff4 && addr < 24'h007ff6;
 assign board_io_cs = addr == 24'h007ff6;
 assign mm_cs2 = addr == 24'h007ff7;
+assign sd_cs = addr >= 24'h007ff8 && addr < 24'h007ffd;
 assign irq_cs  = addr == 24'h007fff;
 
 endmodule