State (computer science)

About: State (computer science) is a research topic. Over the lifetime, 24436 publications have been published within this topic receiving 225733 citations.

Method of programming phase-change memory element

Abstract: A method of programming an electrically programmable phase-change memory element to the low resistance state. A first pulse of energy sufficient to transform the device from the low to high resistance states is applied, and a second pulse of energy sufficient to transform the device from the high to low resistance states is applied following the first pulse. In another programming method, the present and desired device states are compared, and programming pulses are applied only if the state of the device needs to be changed.

Nonvolatile multilevel memories for digital applications

Abstract: When thinking of semiconductor memories, it comes naturally to associate stored bits and memory cells with a one-to-one relationship. That, however, is not really a must nor necessarily the most convenient solution for data storage, since using analog signals and digital-to-analog (D/A) as well as analog-to digital (A/D) conversions a large number of bits could be memorized in a single cell, although, of course, the use of analog signals presents all drawbacks of signal-to-noise ratio that are so well known in electronics. In fact, the real question in this sense concerns the number of bits used for the A/D and D/A conversions, since the conventional (fully) digital case can be seen as the simplest realization of a general approach tending to infinitely precise analog storage (i.e. an infinite number of stored bits per cell) at the other extreme. Naturally, in the real world the conflicting aspects of density (measured in bits per cell) and noise immunity (in a general sense) should be traded off one against the other looking for optimum use of silicon area, of course depending on technology, architectures, circuits and reliability. From this point of view it is obvious that the fully digital approach based on the one-bit one-cell concept does not represent necessarily the best solution. Recently, this general question has assumed real and practical significance for nonvolatile memories, since devices storing two bits per cell are now being introduced on the market. At the same time, in a number of research labs a significant effort is currently being dedicated to the study of the limits and practical convenience of storage density considering the current state of the art in technology and circuit designs. This problem, however, presents a number of interacting aspects concerning cell concept, programming and reading schemes, and architectures and reliability that are of interest well beyond the field of nonvolatile memories, because they are ultimately dealing with the basic question of analog versus digital signals. In this contrast, the present paper considers the question of multilevel nonvolatile memories in all its interacting aspects, analyzing both the current state of the art and the future possibilities.

System for remote computer control using message broadcasting system

Abstract: A system for remote control of a mobile computer system from a base computer system, where the base system generates control command tokens which are broadcast over a pager system. A communicator including a pager receiver, which is normally in a standby state, is connected to the mobile computer, which is normally in an off state, and receives the command tokens. Stored in both the base computer and the mobile computer is a table of commands, cross-referenced with the command tokens. The command tokens are used to instruct the mobile computer to take a variety of actions, including telephoning the base computer, informing the base computer of the mobile computer's location, exchanging file update information and application version information, and other actions requiring communication between the base station and the remote station. The communicator includes a local CPU and SRAM, and powers up the mobile computer as necessary. Certain commands and information exchange may be carried out by the local CPU without powering up the mobile computer.

Understanding Java stack inspection

Abstract: Current implementations of Java make security decisions by searching the runtime call stack. These systems have attractive security properties, but they have been criticized as being dependent on specific artifacts of the Java implementation. The paper models the stack inspection algorithm in terms of a well understood logic for access control and demonstrates how stack inspection is a useful tool for expressing and managing complex trust relationships. We show that an access control decision based on stack inspection corresponds to the construction of a proof in the logic, and we present an efficient decision procedure for generating these proofs. By examining the decision procedure, we demonstrate that many statements in the logic are equivalent and can thus be expressed in a simpler form. We show that there are a finite number of such statements, allowing us to represent the security state of the system as a pushdown automaton. We also show that this automaton may be embedded in Java by rewriting all Java classes to pass an additional argument when a procedure is invoked. We call this security passing style and describe its benefits over previous stack inspection systems. Finally, we show how the logic allows us to describe a straightforward design for extending stack inspection across remote procedure calls.

High speed microcomputer in-circuit emulator

Abstract: An in-circuit emulator (ICE) for hardware/software development and debugging microprocessors. Program execution reconstruction is extracted from an on-board cache memory. An external ICE enclosure interfaces to a target system microprocessor via a cable and a buffer/interface pod. A control program directs a non-intrusive emulation and a monitor program resides in a personal computer host and supports ICE commands. The monitor program allows a user to follow a target system's program flow, to capture related processor information, to make program modifications, and allows the user to restart programs. An on-line disassembler presents a display so as to allow the designer to examine memory, using instruction mnemonics rather than hexadecimal values, thus improving the designer's ability to read program memory. A bit trace buffer records the state of each the microprocessor's signals during each cycle of each instruction. Multiple breakpoints allow a system developer to control a program in ROM, as well as one resident in RAM. An external-range hardware breakpoint and up to sixteen software breakpoints are provided and these allow a designer to display, set and reset breakpoint addresses.