ID protected memory with a maskable ID template

Access circuitry associated with a peripheral device for selectively gaining access thereto from the common data link, comprising:

• interface means for interfacing with the common data link for receiving ID information and control information from a common data link and transferring data between the common data link and the peripheral unit;
• protocol means for receiving and storing control information and ID information received from the common data link;
• ID storage means for storing a digital ID template corresponding to the ID information;
• data transfer means for transferring data between said interface means and the peripheral device;
• masking means for masking off a portion of said ID template in response to receiving a predetermined mask command in the control information, said predetermined mask command determining the portion of said ID template that is masked off;
• compare means for comparing the unmasked portion of said ID template with the corresponding portion of the received ID information stored in said protocol means and outputting a match signal if a match is present between the unmasked portion of said ID template and the corresponding portion of the received ID information stored in said protocol means;
• control means for controlling said data transfer means to transfer data to the peripheral device from said interface means in response to device Write control information stored in said protocol means, or from the peripheral device to said interface means in response to device Read control information stored in said protocol means;
• inhibit means for inhibiting access to the peripheral unit by said data transfer means if a match signal is not generated by said compare means.