diff --git a/ChangeLog b/ChangeLog
index 4f17cf5..904f846 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,7 +1,10 @@
 2017-04-28  NIIBE Yutaka  <gniibe@fsij.org>
 
-	* src/usb_ctrl.c (download_check_crc32): Use check_crc32.
 	* src/mcu-stm32f103.c: New.
+	(check_crc32, sram_address): New.
+
+	* src/usb_ctrl.c (download_check_crc32): Use check_crc32 and
+	sram_address.
 
 	* src/openpgp-do.c (gpg_write_digital_signature_counter): Fix
 	writing lower 10-bit.
diff --git a/emulation/Makefile b/emulation/Makefile
new file mode 100644
index 0000000..bfa6499
--- /dev/null
+++ b/emulation/Makefile
@@ -0,0 +1,31 @@
+SRCS = usbip-server.c
+OBJS = $(SRCS:.c=.o)
+TARGET=gnuk_emulation
+GNUKDIR=../src
+
+GNUK_SRCS = main.c call-rsa.c \
+	usb-ccid.c openpgp.c ac.c openpgp-do.c flash.c \
+	bn.c mod.c \
+	modp256r1.c jpc_p256r1.c ec_p256r1.c call-ec_p256r1.c \
+	modp256k1.c jpc_p256k1.c ec_p256k1.c call-ec_p256k1.c \
+	mod25638.c ecc-edwards.c ecc-mont.c sha512.c \
+	random.c neug.c sha256.c
+USB_SRCS=usb_desc.c usb_ctrl.c 
+
+GNUK_CSRC = $(addprefix $(GNUKDIR)/, $(GNUK_SRCS))
+GNUK_OBJS = $(notdir $(GNUK_CSRC:.c=.o))
+
+USB_CSRC = $(addprefix $(GNUKDIR)/, $(USB_SRCS))
+USB_OBJS = $(notdir $(USB_CSRC:.c=.o))
+
+# all:
+# 	echo $(GNUK_OBJS)
+
+$(TARGET): $(OBJS) $(USB_OBJS) Makefile
+	$(CC) -o $(TARGET) $(OBJS) $(USB_OBJS)
+
+$(GNUK_OBJS): %.o : $(GNUKDIR)/%.c Makefile
+	$(CC) -c $(CFLAGS) -I. -I$(GNUKDIR) -I../chopstx $< -o $@
+
+$(USB_OBJS): %.o : $(GNUKDIR)/%.c Makefile
+	$(CC) -c $(CFLAGS) -I. -I$(GNUKDIR) -I../chopstx $< -o $@
diff --git a/src/gnuk.h b/src/gnuk.h
index b5eb15a..55ae8e1 100644
--- a/src/gnuk.h
+++ b/src/gnuk.h
@@ -461,3 +461,4 @@ int pinpad_getline (int msg_code, uint32_t timeout_usec);
 extern uint8_t _regnual_start, __heap_end__[];
 
 int check_crc32 (const uint32_t *start_p, const uint32_t *end_p);
+uint8_t * sram_address (uint32_t offset);
diff --git a/src/mcu-stm32f103.c b/src/mcu-stm32f103.c
index 5ccedc6..ce10515 100644
--- a/src/mcu-stm32f103.c
+++ b/src/mcu-stm32f103.c
@@ -48,3 +48,9 @@ check_crc32 (const uint32_t *start_p, const uint32_t *end_p)
 
   return (rbit (CRC->DR) ^ crc32) == 0xffffffff;
 }
+
+uint8_t *
+sram_address (uint32_t offset)
+{
+  return ((uint8_t *)0x20000000) + offset;
+}
diff --git a/src/usb_ctrl.c b/src/usb_ctrl.c
index bbb1c6d..3e89c42 100644
--- a/src/usb_ctrl.c
+++ b/src/usb_ctrl.c
@@ -233,8 +233,7 @@ usb_setup (struct usb_dev *dev)
 	}
       else /* SETUP_SET */
 	{
-	  uint8_t *addr = (uint8_t *)(0x20000000 + arg->value * 0x100
-				      + arg->index);
+	  uint8_t *addr = sram_address ((arg->value * 0x100) + arg->index);
 
 	  if (arg->request == USB_FSIJ_GNUK_DOWNLOAD)
 	    {
@@ -255,7 +254,7 @@ usb_setup (struct usb_dev *dev)
 	      if (*ccid_state_p != CCID_STATE_EXITED)
 		return -1;
 
-	      if (((uint32_t)addr & 0x03))
+	      if (((uintptr_t)addr & 0x03))
 		return -1;
 
 	      return download_check_crc32 (dev, (uint32_t *)addr);