Abstract: A memory management unit (MMU) having cross-domain control for controlling a CPU's right to access a memory in order to initiate performance of an operation. The MMU includes a translator for translating a virtual address issued by the CPU into a physical address, a data domain number (DDN) and an address domain number (ADN) both corresponding to a domain (a portion of the virtual address space), and a permission. The MMU further includes an environment controller for determining if the ADN corresponding to the operation is allowed access by the CPU. The translator includes an address translation unit (ATU), a data translation unit (DTU), translation table lookup logic, and permission control logic. The ATU generates the physical address, the ADN, and the permission from the virtual address. The DTU generates the DDN of tagged data specified by the CPU if the tagged data is a pointer. The TTLL supplies entry information to the ATU and DTU.

Abstract: A system and method for writing reference information on a recording media contained with a sealed housing utilizes a reflective planar mirror on the rotary actuator controlling the writing mechanism. A narrow beam directed through a window on the side wall of the housing onto the mirror is reflected off at angle dependent on the actuator position to a beam sensitive detector. A translator system driven by a positioner disposed at a distance from the rotary actuator axis which is substantially greater than the distance between the actuator axis and the writing head, is used to vary the relationship between the directed and reflected beams. This system incorporates the rotary actuator in a closed loop servo that positions the actuator precisely at different locations relative to the recording medium, so that the reference information may be written.