diff --git a/cpu/z80/dev/rs232.c b/cpu/z80/dev/rs232.c
index b785ded39..4b7cd924e 100644
--- a/cpu/z80/dev/rs232.c
+++ b/cpu/z80/dev/rs232.c
@@ -27,7 +27,7 @@
  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.  
  *
- * $Id: rs232.c,v 1.2 2007/09/11 12:03:20 matsutsuka Exp $
+ * $Id: rs232.c,v 1.3 2007/09/19 12:47:55 matsutsuka Exp $
  *
  */
 /*
@@ -48,7 +48,7 @@ PROCESS_THREAD(rs232_process, ev, data)
 {
   static struct etimer timer;
   char ch;
-  unsigned char i;
+  unsigned char i, stat;
   PROCESS_BEGIN();
 
   rs232_arch_init(RS232_BAUD_RATE);
@@ -59,8 +59,8 @@ PROCESS_THREAD(rs232_process, ev, data)
 
     if (etimer_expired(&timer)) {
       for (i = 0; i < RS232_BUFSIZE; i++) {
-	ch = rs232_arch_poll();
-	if (ch == 0) {
+	ch = rs232_arch_poll(&stat);
+	if (stat == 0) {
 	  break;
 	}
 	/* We have an input data */
diff --git a/cpu/z80/dev/rs232.h b/cpu/z80/dev/rs232.h
index d2c29c3c4..4ec951952 100644
--- a/cpu/z80/dev/rs232.h
+++ b/cpu/z80/dev/rs232.h
@@ -27,7 +27,7 @@
  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.  
  *
- * $Id: rs232.h,v 1.2 2007/09/11 12:03:20 matsutsuka Exp $
+ * $Id: rs232.h,v 1.3 2007/09/19 12:47:55 matsutsuka Exp $
  *
  */
 /*
@@ -51,9 +51,9 @@ void rs232_arch_init(unsigned long ubr);
 
 /*
  * An architecture-depend implementation of RS-232C polling.
- * @return character, zero if no input.
+ * @return character, stat == zero if no input.
  */
-unsigned char rs232_arch_poll(void);
+unsigned char rs232_arch_poll(unsigned char* stat);
 
 /*
  * An architecture-depend implementation of RS-232C writing a byte.
diff --git a/platform/pc-6001/dev/rs232-asm.S b/platform/pc-6001/dev/rs232-asm.S
index f57799d9f..9a17db01c 100644
--- a/platform/pc-6001/dev/rs232-asm.S
+++ b/platform/pc-6001/dev/rs232-asm.S
@@ -7,7 +7,7 @@
 ;;; 
 ;;; @author Takahide Matsutsuka <markn@markn.org>
 ;;; 
-;;; $Id: rs232-asm.S,v 1.1 2007/09/11 12:12:59 matsutsuka Exp $
+;;; $Id: rs232-asm.S,v 1.2 2007/09/19 12:47:19 matsutsuka Exp $
 ;;; 
 	
 	;; definitions of PC-6001 BIOS routines
@@ -37,18 +37,25 @@ _rs232_arch_writeb:
 	ret
 
 	;; ---------------------------------
-	;; unsigned char rs232_arch_poll();
-	;; Stack; retl reth
-	;; AFBC__HL____
-	;; return input byte (zero if no input)
+	;; unsigned char rs232_arch_poll(unsigned char *stat);
+	;; Stack; retl reth statl stath
+	;; AFBCDEHL____
+	;; return input byte (*stat == 0 if no input)
 	;; ---------------------------------
 _rs232_arch_poll:
-	ld	a,#0x01
+	ld	hl, #2
+	add	hl, sp
+	ld	e, (hl)
+	inc	hl
+	ld	d, (hl)
+	ld	a, #0x01
+	ld	(de), a
 	di
 	call	#_char_input_sub	; read from buffer
 	ei
 	jr	nz, _rs232_arch_poll_ret
 	xor	a			; we have no data in the buffer
+	ld	(de), a
 _rs232_arch_poll_ret:
 	ld	l, a
 	ret