diff --git a/main.cpp b/main.cpp
index 8ca0573..7f445f2 100644
--- a/main.cpp
+++ b/main.cpp
@@ -255,7 +255,7 @@ int main(int argc, char *argv[])
 
 	running = cnsl->get_running_flag();
 
-	tty *tty_ = new tty(cnsl);
+	tty *tty_ = new tty(cnsl, b);
 
 	b->add_tty(tty_);
 
diff --git a/tty.cpp b/tty.cpp
index 688f16b..5aeacef 100644
--- a/tty.cpp
+++ b/tty.cpp
@@ -1,10 +1,11 @@
-// (C) 2018 by Folkert van Heusden
+// (C) 2018-2023 by Folkert van Heusden
 // // Released under Apache License v2.0
 #include <errno.h>
 #include <string.h>
 #include <unistd.h>
 
 #include "tty.h"
+#include "cpu.h"
 #include "gen.h"
 #include "log.h"
 #include "memory.h"
@@ -18,7 +19,9 @@ const char * const regnames[] = {
 	"puncher buffer"
 	};
 
-tty::tty(console *const c) : c(c)
+tty::tty(console *const c, bus *const b) :
+	c(c),
+	b(b)
 {
 }
 
@@ -65,7 +68,7 @@ uint16_t tty::readWord(const uint16_t addr)
 		}
 	}
 	else if (addr == PDP11TTY_TPS) {
-		vtemp = 128;
+		vtemp |= 128;
 	}
 
 	DOLOG(debug, true, "PDP11TTY read addr %o (%s): %d, 7bit: %d", addr, regnames[reg], vtemp, vtemp & 127);
@@ -103,6 +106,11 @@ void tty::writeWord(const uint16_t addr, uint16_t v)
 		DOLOG(debug, true, "PDP11TTY print '%c'", ch);
 
 		c->put_char(ch);
+
+		registers[(PDP11TTY_TPS - PDP11TTY_BASE) / 2] |= 128;
+
+		if (registers[(PDP11TTY_TPS - PDP11TTY_BASE) / 2] & 64)
+			b->getCpu()->queue_interrupt(4, 064);
 	}
 
 	DOLOG(debug, true, "set register %o to %o", addr, v);
diff --git a/tty.h b/tty.h
index abe6090..33f230f 100644
--- a/tty.h
+++ b/tty.h
@@ -1,4 +1,4 @@
-// (C) 2018-2022 by Folkert van Heusden
+// (C) 2018-2023 by Folkert van Heusden
 // Released under Apache License v2.0
 #pragma once
 
@@ -6,6 +6,7 @@
 #include <stdio.h>
 #include <string>
 
+#include "bus.h"
 #include "console.h"
 
 
@@ -22,12 +23,13 @@ class tty
 {
 private:
 	console *const c      { nullptr };
+	bus     *const b      { nullptr };
 	bool     have_char_1  { false };  // RCVR BUSY bit high (11)
 	bool     have_char_2  { false };  // RCVR DONE bit high (7)
 	uint16_t registers[4] { 0 };
 
 public:
-	tty(console *const c);
+	tty(console *const c, bus *const b);
 	virtual ~tty();
 
 	uint8_t readByte(const uint16_t addr);