DOS application programs are accommodated when using a controllerless modem by providing a virtual device driver. The virtual device driver emulates UART to UART communications and handles interrupts by the DOS applications and by a hardware port managed by the controllerless modem. In one implementation,...http://www.google.com.tw/patents/US6230118?utm_source=gb-gplus-share專利 US6230118 - DOS based application supports for a controllerless modem
