diff --git a/acia.cpp b/acia.cpp
new file mode 100644
index 0000000..a6cfdde
--- /dev/null
+++ b/acia.cpp
@@ -0,0 +1,21 @@
+#include <stdint.h>
+
+#include "memory.h"
+#include "acia.h"
+
+void acia::operator=(uint8_t b) {
+	if (_acc & 1) {
+		_device->write(b);
+		return;
+	}
+	if ((b & cd_mask) == 0x03)
+		_device->reset();
+	// FIXME: more
+}
+
+acia::operator uint8_t() {
+	if (_acc & 1)
+		return _device->read();
+
+	return _device->more()? rdrf | tdre: 0;
+}