Apparatus and method for providing access security to a device coupled upon a two-wire bidirectional bus

Abstract

A computer system, bus interface unit, and method are provided for securing certain devices connected to an I C bus. Those devices include any device which contains sensitive information or passwords. For example, a device controlled by a I C-connected device bay controller may contain sensitive files, data, and information to which improper access may be denied by securing the device bay controller. Moreover, improper accesses to passwords contained in non-volatile memory connected to the I C bus must also be prevented. A bus interface unit coupled within the computer contains registers, and logic which compares the incoming I C target and word addresses with coded bits within fields of those registers. If the target or word address is to a protected address or range of addresses, then an unlock signal must be issued before the security control logic will allow the target or word address to access the I C bus or addressed device thereon. The unlock signal can be assigned to a particular slot among numerous slots, wherein the slots are arranged in hierarchical order. This allows a system administrator the capability to unlock accesses to protected non-volatile memory, and thereby allowing the system administrator to change passwords within one portion of non-volatile memory, and possibly allowing a lower priority user to access and change a password within another portion of non-volatile memory. The slot which accommodates an unlock signal assigned to the system administrator is altogether separate from a slot assigned to a non-system administrator or user.