diff --git a/hardware.h b/hardware.h
index 0e2c9f3..2455890 100644
--- a/hardware.h
+++ b/hardware.h
@@ -25,4 +25,10 @@ extern class spiram sram;
 extern class Memory memory;
 #endif
 
+#if defined(DEBUGGING)
+#define DBG(x) Serial.x
+#else
+#define DBG(x)
+#endif
+
 #endif
diff --git a/pia.cpp b/pia.cpp
index 53ba09d..d35ea9b 100644
--- a/pia.cpp
+++ b/pia.cpp
@@ -177,3 +177,17 @@ uint8_t PIA::read_portb() {
 	irq_b1 = irq_b2 = false;
 	return (inb & ~ddrb) | (outb & ddrb);
 }
+
+void PIA::write_porta_in_bit(uint8_t mask, bool state) {
+	if (state)
+		ina |= mask;
+	else
+		ina &= ~mask;
+}
+
+void PIA::write_portb_in_bit(uint8_t mask, bool state) {
+	if (state)
+		inb |= mask;
+	else
+		inb &= ~mask;
+}
diff --git a/pia.h b/pia.h
index 8104ff1..4b13a0d 100644
--- a/pia.h
+++ b/pia.h
@@ -23,9 +23,11 @@ public:
 
 	// device input (external) interface
 	void write_porta_in(uint8_t b) { ina = b; }
+	void write_porta_in_bit(uint8_t, bool);
 	void write_ca1(bool);
 	void write_ca2(bool);
 	void write_portb_in(uint8_t b) { inb = b; }
+	void write_portb_in_bit(uint8_t, bool);
 	void write_cb1(bool);
 	void write_cb2(bool);