diff --git a/src/main/scala/device/AXI4DummySD.scala b/src/main/scala/device/AXI4DummySD.scala
index a0b90f35ded95057e801f2faec08fe3e49775a9c..85010198066a24cacd7ee1d07f22d22c9400ca52 100644
--- a/src/main/scala/device/AXI4DummySD.scala
+++ b/src/main/scala/device/AXI4DummySD.scala
@@ -32,23 +32,22 @@ class SDHelper extends BlackBox with HasBlackBoxInline {
   setInline("SDHelper.v",
     s"""
        |import "DPI-C" function void sd_setaddr(input int addr);
-       |import "DPI-C" function int sd_read(input bit ren);
+       |import "DPI-C" function void sd_read(output int data);
        |
        |module SDHelper (
        |  input clk,
        |  input setAddr,
        |  input [31:0] addr,
        |  input ren,
-       |  output [31:0] data
+       |  output reg [31:0] data
        |);
        |
-       |  always @(posedge clk) begin
-       |    if (setAddr) begin
-       |      sd_setaddr(addr);
-       |    end
+       |  always @(negedge clk) begin
+       |    if (ren) sd_read(data);
+       |  end
+       |  always@(posedge clk) begin
+       |    if (setAddr) sd_setaddr(addr);
        |  end
-       |
-       |  assign data = sd_read(ren);
        |
        |endmodule
      """.stripMargin)
diff --git a/src/test/csrc/sdcard.cpp b/src/test/csrc/sdcard.cpp
index 3d74fa5020a4f44f4e98cb62561dbd5adebe4df8..8abe9c7475a39efeef7d8e059a0c536e1afa1074 100644
--- a/src/test/csrc/sdcard.cpp
+++ b/src/test/csrc/sdcard.cpp
@@ -11,18 +11,14 @@ void sd_setaddr(uint32_t addr) {
   //assert(0);
 }
 
-uint32_t sd_read(int ren) {
-  if (ren) {
-    uint32_t data;
-    fread(&data, 4, 1, fp);
-    //printf("read data = 0x%08x\n", *data);
-    return data;
-  }
-  return 0xdeadbeaf;
+void sd_read(uint32_t *data) {
+  fread(data, 4, 1, fp);
+  //printf("read data = 0x%08x\n", *data);
+  //assert(0);
 }
 
 void init_sd(void) {
-  fp = fopen("/home/xyn/debian/debian.img", "r");
+  fp = fopen("/home/xyn/workloads/debian/riscv-debian.img", "r");
   if(!fp)
   {
     eprintf(ANSI_COLOR_MAGENTA "[warning] sdcard img not found\n");