diff --git a/sim/erc32/erc32.c b/sim/erc32/erc32.c
index 03b40dc..4584957 100644
--- a/sim/erc32/erc32.c
+++ b/sim/erc32/erc32.c
@@ -22,6 +22,7 @@
 /* The control space devices */
 
 #include "config.h"
+#include <errno.h>
 #include <sys/types.h>
 #include <stdio.h>
 #include <string.h>
@@ -39,6 +40,7 @@ extern int      rom8,wrp,uben;
 extern char     uart_dev1[], uart_dev2[];
 
 int dumbio = 0; /* normal, smart, terminal oriented IO by default */
+int tty_setup = 1; /* default setup if not a tty */
 
 /* MEC registers */
 #define MEC_START 	0x01f80000
@@ -301,12 +303,15 @@ static void	store_bytes (unsigned char *mem, uint32 waddr,
 
 extern int	ext_irl;
 
+static host_callback *callback;
+
 
 /* One-time init */
 
 void
 init_sim()
 {
+    callback = sim_callback;
     port_init();
 }
 
@@ -944,10 +949,14 @@ init_stdio()
 {
     if (dumbio)
         return; /* do nothing */
-    if (!ifd1)
+    if (ifd1 == 0 && f1open) {
 	tcsetattr(0, TCSANOW, &ioc1);
-    if (!ifd2)
+        tcflush(ifd1, TCIFLUSH);
+    }
+    if (ifd2 == 0 && f1open) {
 	tcsetattr(0, TCSANOW, &ioc2);
+        tcflush(ifd2, TCIFLUSH);
+    }
 }
 
 void
@@ -955,16 +964,18 @@ restore_stdio()
 {
     if (dumbio)
         return; /* do nothing */
-    if (!ifd1)
+    if (ifd1 == 0 && f1open && tty_setup)
 	tcsetattr(0, TCSANOW, &iocold1);
-    if (!ifd2)
+    if (ifd2 == 0 && f2open && tty_setup)
 	tcsetattr(0, TCSANOW, &iocold2);
 }
 
 #define DO_STDIO_READ( _fd_, _buf_, _len_ )          \
-             ( dumbio                                \
+             ( dumbio || nouartrx \
                ? (0) /* no bytes read, no delay */   \
-               : read( _fd_, _buf_, _len_ ) )
+               : (_fd_) == 1 && callback ? \
+                 callback->read_stdin (callback, _buf_, _len_) :  \
+                 read( _fd_, _buf_, _len_ ) )
 
 
 static void
@@ -994,21 +1005,26 @@ port_init()
 	}
     if (f1in) ifd1 = fileno(f1in);
     if (ifd1 == 0) {
+        if (callback && !callback->isatty(callback, ifd1)) {
+            tty_setup = 0;
+        }
 	if (sis_verbose)
 	    printf("serial port A on stdin/stdout\n");
         if (!dumbio) {
             tcgetattr(ifd1, &ioc1);
+            if (tty_setup) {
             iocold1 = ioc1;
             ioc1.c_lflag &= ~(ICANON | ECHO);
             ioc1.c_cc[VMIN] = 0;
             ioc1.c_cc[VTIME] = 0;
         }
+        }
 	f1open = 1;
     }
 
     if (f1out) {
 	ofd1 = fileno(f1out);
-    	if (!dumbio && ofd1 == 1) setbuf(f1out, NULL);
+    	if (!dumbio && tty_setup && ofd1 == 1) setbuf(f1out, NULL);
     }
 
     if (uart_dev2[0] != 0)
@@ -1027,17 +1043,19 @@ port_init()
 	    printf("serial port B on stdin/stdout\n");
         if (!dumbio) {
             tcgetattr(ifd2, &ioc2);
+            if (tty_setup) {
             iocold2 = ioc2;
             ioc2.c_lflag &= ~(ICANON | ECHO);
             ioc2.c_cc[VMIN] = 0;
             ioc2.c_cc[VTIME] = 0;
         }
+        }
 	f2open = 1;
     }
 
     if (f2out) {
 	ofd2 = fileno(f2out);
-        if (!dumbio && ofd2 == 1) setbuf(f2out, NULL);
+        if (!dumbio && tty_setup && ofd2 == 1) setbuf(f2out, NULL);
     }
 
     wnuma = wnumb = 0;
@@ -1066,6 +1084,9 @@ read_uart(addr)
 	    if (f1open) {
 	        anum = DO_STDIO_READ(ifd1, aq, UARTBUF);
 	    }
+      else {
+          anum = 0;
+      }
 	    if (anum > 0) {
 		aind = 0;
 		if ((aind + 1) < anum)
@@ -1098,6 +1119,9 @@ read_uart(addr)
 	    if (f2open) {
 		bnum = DO_STDIO_READ(ifd2, bq, UARTBUF);
 	    }
+	    else {
+		bnum = 0;
+	    }
 	    if (bnum > 0) {
 		bind = 0;
 		if ((bind + 1) < bnum)
@@ -1130,6 +1154,9 @@ read_uart(addr)
 	    if (f1open) {
 	        anum = DO_STDIO_READ(ifd1, aq, UARTBUF);
             }
+	    else {
+		anum = 0;
+	    }
 	    if (anum > 0) {
 		Ucontrol |= 0x00000001;
 		aind = 0;
@@ -1142,6 +1169,9 @@ read_uart(addr)
 	    if (f2open) {
 		bnum = DO_STDIO_READ(ifd2, bq, UARTBUF);
 	    }
+	    else {
+		bnum = 0;
+	    }
 	    if (bnum > 0) {
 		Ucontrol |= 0x00010000;
 		bind = 0;
@@ -1182,8 +1212,12 @@ write_uart(addr, data)
 	    if (wnuma < UARTBUF)
 	        wbufa[wnuma++] = c;
 	    else {
-	        while (wnuma)
+	        while (wnuma) {
+              if (ofd1 == 1 && callback)
+                  wnuma -= callback->write_stdout(callback, wbufa, wnuma);
+              else
 		    wnuma -= fwrite(wbufa, 1, wnuma, f1out);
+          }
 	        wbufa[wnuma++] = c;
 	    }
 	}
@@ -1206,8 +1240,12 @@ write_uart(addr, data)
 	    if (wnumb < UARTBUF)
 		wbufb[wnumb++] = c;
 	    else {
-		while (wnumb)
+          while (wnumb) {
+              if (ofd1 == 1 && callback)
+                  wnumb -= callback->write_stdout(callback, wbufb, wnumb);
+              else
 		    wnumb -= fwrite(wbufb, 1, wnumb, f2out);
+          }
 		wbufb[wnumb++] = c;
 	    }
 	}
@@ -1245,19 +1283,37 @@ write_uart(addr, data)
 static void
 flush_uart()
 {
-    while (wnuma && f1open)
+    while (wnuma && f1open) {
+        if (ofd1 == 1 && callback) {
+            wnuma -= callback->write_stdout(callback, wbufa, wnuma);
+            callback->flush_stdout(callback);
+        }
+        else
 	wnuma -= fwrite(wbufa, 1, wnuma, f1out);
-    while (wnumb && f2open)
+    }
+    while (wnumb && f2open) {
+        if (ofd2 == 1 && callback) {
+            wnuma -= callback->write_stdout(callback, wbufb, wnuma);
+            callback->flush_stdout(callback);
+        }
+        else
 	wnumb -= fwrite(wbufb, 1, wnumb, f2out);
 }
+}
 
 
 
 static void
 uarta_tx()
 {
-
-    while (f1open && fwrite(&uarta_sreg, 1, 1, f1out) != 1);
+    while (f1open) {
+        if (ofd1 == 1 && callback) {
+            while (callback->write_stdout(callback, &uarta_sreg, 1) != 1);
+        }
+        else {
+            while (fwrite(&uarta_sreg, 1, 1, f1out) != 1);
+        }
+    }
     if (uart_stat_reg & UARTA_HRE) {
 	uart_stat_reg |= UARTA_SRE;
     } else {
@@ -1271,7 +1327,14 @@ uarta_tx()
 static void
 uartb_tx()
 {
-    while (f2open && fwrite(&uartb_sreg, 1, 1, f2out) != 1);
+    while (f2open) {
+        if (ofd2 == 1 && callback) {
+            while (callback->write_stdout(callback, &uarta_sreg, 1) != 1);
+        }
+        else {
+            while (fwrite(&uartb_sreg, 1, 1, f2out) != 1);
+        }
+    }
     if (uart_stat_reg & UARTB_HRE) {
 	uart_stat_reg |= UARTB_SRE;
     } else {
@@ -1293,6 +1356,8 @@ uart_rx(arg)
     rsize = 0;
     if (f1open)
         rsize = DO_STDIO_READ(ifd1, &rxd, 1);
+    else
+        rsize = 0;
     if (rsize > 0) {
 	uarta_data = UART_DR | rxd;
 	if (uart_stat_reg & UARTA_HRE)
@@ -1309,6 +1374,8 @@ uart_rx(arg)
     rsize = 0;
     if (f2open)
         rsize = DO_STDIO_READ(ifd2, &rxd, 1);
+    else
+        rsize = 0;
     if (rsize) {
 	uartb_data = UART_DR | rxd;
 	if (uart_stat_reg & UARTB_HRE)
diff --git a/sim/erc32/func.c b/sim/erc32/func.c
index 70b42c9..440bff1 100644
--- a/sim/erc32/func.c
+++ b/sim/erc32/func.c
@@ -52,6 +52,8 @@ char            uart_dev1[128] = "";
 char            uart_dev2[128] = "";
 extern	int	ext_irl;
 uint32		last_load_addr = 0;
+int		nouartrx = 0;
+host_callback 	*sim_callback;
 
 #ifdef ERRINJ
 uint32		errcnt = 0;
diff --git a/sim/erc32/interf.c b/sim/erc32/interf.c
index 981aa11..004d0bb 100644
--- a/sim/erc32/interf.c
+++ b/sim/erc32/interf.c
@@ -61,8 +61,6 @@ extern char     uart_dev1[], uart_dev2[];
 
 int             sis_gdb_break = 1;
 
-host_callback *sim_callback;
-
 int
 run_sim(sregs, icount, dis)
     struct pstate  *sregs;
@@ -209,6 +207,9 @@ sim_open (kind, callback, abfd, argv)
             if (strcmp(argv[stat], "-dumbio") == 0) {
 		dumbio = 1;
 	    } else
+            if (strcmp(argv[stat], "-nouartrx") == 0) {
+		nouartrx = 1;
+	    } else
             if (strcmp(argv[stat], "-wrp") == 0) {
                 wrp = 1;
 	    } else
diff --git a/sim/erc32/sis.c b/sim/erc32/sis.c
index e109874..1f834a0 100644
--- a/sim/erc32/sis.c
+++ b/sim/erc32/sis.c
@@ -211,6 +211,8 @@ main(argc, argv)
 #endif
             } else if (strcmp(argv[stat], "-dumbio") == 0) {
 		dumbio = 1;
+            } else if (strcmp(argv[stat], "-nouartrx") == 0) {
+		nouartrx = 1;
             } else if (strcmp(argv[stat], "-v") == 0) {
 		sis_verbose += 1;
 	    } else {
diff --git a/sim/erc32/sis.h b/sim/erc32/sis.h
index 4ecf885..5226666 100644
--- a/sim/erc32/sis.h
+++ b/sim/erc32/sis.h
@@ -169,7 +169,7 @@ struct irqcell {
 /* Prototypes  */
 
 /* erc32.c */
-extern void	init_sim (void);
+extern void	init_sim ();
 extern void	reset (void);
 extern void	error_mode (uint32 pc);
 extern void	sim_halt (void);
@@ -210,6 +210,8 @@ extern void	reset_all (void);
 extern void	sys_reset (void);
 extern void	sys_halt (void);
 extern double	get_time (void);
+extern int	nouartrx;
+extern host_callback *sim_callback;
 
 /* exec.c */
 extern int	dispatch_instruction (struct pstate *sregs);
