diff --git a/chip-z80/nodenames.js b/chip-z80/nodenames.js
index 2dfdbc8..7981949 100644
--- a/chip-z80/nodenames.js
+++ b/chip-z80/nodenames.js
@@ -21,7 +21,11 @@ ab15: 20,
 _reset: 21,
 _wait: 22,
 _int: 23,
+int: 23,
+_irq: 23,
+irq: 23,
 _nmi: 24,
+nmi: 24,
 _busrq: 25,
 _m1: 26,
 _rd: 27,
diff --git a/chip-z80/support.js b/chip-z80/support.js
index b5a2666..f8859dd 100644
--- a/chip-z80/support.js
+++ b/chip-z80/support.js
@@ -110,7 +110,14 @@ var state        = 0;
 var last_rd_done = 1;
 
 function handleBusRead(){
-    if(!isNodeHigh(nodenames['_rd'])){
+    if(!isNodeHigh(nodenames['_m1']) && !isNodeHigh(nodenames['_iorq'])) {
+        // Interrupt acknownledge cycle, force 0xFF onto the bus
+        // In IM0 this is seen as RST 0x38
+        // In IM1 this is ignored
+        // In IM2 this is used as the low byte of the vector
+        // TODO: ideally this "vector" would be a configurable parameter
+        writeDataBus(0xff);
+    } else if(!isNodeHigh(nodenames['_rd'])){
         var a = readAddressBus();
         var d = eval(readTriggers[a]);
         if(d == undefined)