Abstract: A microcontroller (20) provides security for internal instructions and data while allowing instruction fetches to external, off-chip memory connected to an expansion bus (30). A central processing unit (CPU) (21) provides a load instruction register signal to indicate when an access is an instruction fetch. When the load instruction register signal is active while the address is within the range of an on-chip nonvolatile memory (25), a security logic circuit (40) is reset to a first state. In this first state, the security logic circuit (40) also allows non-instruction fetches from the nonvolatile memory (25). However when the load instruction register signal is active while the address is not within the range of the nonvolatile memory (25), the security logic circuit (40) is set to a second state. While in this second state, the security logic circuit (40) disables attempted accesses to the nonvolatile memory (25).

Abstract: A data processor with memory within a single integrated circuit package provides a programmable "secure mode" of operation to selectively restrict access and protect information stored in its memory. The secure mode of operation is included in addition to a "single chip mode" wherein the data processor accesses both data and instructions strictly from within the single integrated circuit package. An "expanded mode" of operation also exists wherein the data processor may access either internal or external memory for both instructions and data. The secure mode of operation restricts accesses of instructions to memory contained within the single integrated circuit while allowing data accesses to memory either internal or external to the integrated circuit. The secure mode is accomplished by selectively isolating internal data/instruction bus transfer activity from an external data/instruction bus.

Abstract: A write protect mechanism for a programmable read-only memory prevents writes to the PROM unless a protect register contains predetermined information. The protect register is itself a write protected control register. The predetermined information cannot be written into the protect register except during a short, predetermined period after the occurrence of an event such as a reset. The protect register may be written to with information other than the predetermined information at any time. The preferred embodiment comprises a single-chip microcomputer with on-board electrically-erasable programmable read-only memory which is write protected in several, separate blocks.

Abstract: A pipe joint in which a metal-to-metal seal is provided on the exterior of the pipe, a torque shoulder provides a further metal-to-metal seal and a still further seal is provided by a resilient ring. The box is protected against ballooning which might result in jump out of the threads by proportioning the thickness of the box at the point of seal at the maximum diameter of seal to the outer diameter of the box as compared to the full wall thickness of the pipe related to the outer diameter of the pipe.

Abstract: A pipe joint in which a metal-to-metal seal is provided on the exterior of the pipe, a torque shoulder provides a further metal-to-metal seal and a still further seal is provided by a resilient ring. The box is protected against ballooning which might result in jump out of the threads by proportioning the thickness of the box at the point of seal at the maximum diameter of seal to the outer diameter of the box as compared to the full wall thickness of the pipe related to the outer diameter of the pipe.

Abstract: A pipe joint with premium threads having both metal-to-metal and polymeric seals to block fluid leakage through the joint. A polymeric seal ring is preferably carried within an annular groove in the box end. Metal sealing surfaces, each having a different inside diameter, are provided on opposite sides of the annular groove to form metal-to-metal seals with two compatible metal sealing surfaces on the exterior of the pin member. The joint is thus characterized by two metal-to-metal seals formed on opposite sides of the annular groove to trap the seal ring therebetween. The metal-to-metal seals cooperate to prevent undesired extrusion of the seal ring.

Abstract: A pipe joint in which a metal-to-metal seal is provided on the exterior of the pipe, a torque shoulder provides a further metal-to-metal seal and a still further seal is provided by a resilient ring. The box is protected against ballooning which might result in jump out of the threads by proportioning the thickness of the box at the point of seal at the maximum diameter of seal to the outer diameter of the box as compared to the full wall thickness of the pipe related to the outer diameter of the pipe.