I/O control system having a plurality of access enabling bits for controlling access to selective parts of an I/O device

摘要

In an I/O port protection device, is described wherein accessing an I/O device is selectively controlled by a value of a bit stored in a bit map. A CPU instruction accessing a port is allowed direct access when the bit value for that port is a zero, but is trapped when the value is a one. A trapped instruction is either prohibited from any accessing or is rerouted for accessing a different I/O port.