Arm Limited

David Michael Gilday

Simon John Craske

Chiloda Ashan Senerath Pathirane

Richard Roy Grisenthwaite

Stuart David Biles

David Hennah Mansell

Daniel Kershaw

Matthew James Horsnell

Balaji Venu

Edmond John Simon Ashfield

Daryl Wayne Bradley

Xabier Iturbe

Peter Logan Harrod

Reiley Jeyapaul

Mittu Xavier Kocherry

An apparatus is provided comprising receiving circuitry to receive a representation of a circuit comprising a plurality of flops. Categorisation circuitry determines data dependencies between the flops from the representation and generates a categorisation of the flops into one of at least: a vulnerable category, a conditional category, and an isolated category, in dependence on the data dependencies. The categorisation indicates the vulnerability of the flops to transient errors. Output circuitry outputs the categorisation of the flops. The conditional category comprises those of the flops whose change in value is indicated by a change in a value in a corresponding flop in the flops or corresponding signal. The vulnerable category comprises those of the flops that are absent from the conditional category and whose change in value is affected by one of the flops or a signal and the isolated category comprises the flops that are absent from the conditional category and that are absent from the vulnerable category.

Vulnerability determination in circuits

A data processing apparatus has at least one circuit block accessible for debugging by a debugger, the block having a set of debug status registers and a debug event register which is set by the circuit block to indicate occurrence of a debug event. Debug interface circuitry interfaces with the set of debug status registers for each circuit block. The circuitry includes at least a first portion which is in a first power domain that remains in a fully powered state while the debugger is connected to the circuitry. Status registers are provided in a second power domain which transitions between the fully powered state and at least one low power state while the debugger is connected to the circuitry. Content of the debug status registers is only accessible to the debugger when the second power domain is in the fully powered state.

Data processing apparatus and method for identifying debug events

A virtually indexed and physically tagged memory is described having a cache way size which can exceed the minimum page table size such that aliased virtual addresses VA within the cache waycan be mapped to the same physical address PA. Aliasing management logicpermits multiple copies of the data from the same physical address to be stored at different virtual indexes within the cache within given or different cache ways.

Alias management within a virtually indexed and physically tagged cache memory

Reset control circuitry is disclosed, for controlling a first reset signal for resetting at least a first portion of a circuit and a further reset signal for resetting at least a second portion of said circuit, said reset control circuitry comprising: an input for receiving an input first reset signal; an input for receiving an input further reset signal; an output for outputting an output first reset signal; and an output for outputting an output further reset signal; said reset control circuitry being responsive to detecting deassertion of said input first reset signal when said input further reset signal is asserted to delay deassertion of said output first reset signal so that said output first reset signal is deasserted at a same time or later than said input further reset signal.

Synchronization of two independent reset signals

A data processing apparatus is disclosed that comprises a pipelined processor, said pipelined processor comprising a processing pipeline for processing instructions in a plurality of stages, at least some of said plurality of stages each comprising storage elements for storing an instruction or decoded instruction being processed in said stage, said storage elements in at least one of said stages comprising settable elements, each of said settable elements being adapted to store a predetermined value in response to a wake up event, said settable elements being arranged such that in response to said wake up event said values stored in said settable elements form an instruction or decoded instruction.

Initialisation of a pipelined processor

The data processing apparatus has processing logic for performing data processing operations and a register bank for storing data associated with the processing logic. The register bank has at least one register group, each register group having a plurality of register sets. The processing logic has an operating state associated with each register group defining how that register group is used, a first operating state being a state in which each register set in the register group is used to support an independent execution thread of the processing logic, and a second operating state being a state in which the register sets of the register group are collectively used to support a single execution thread of the processing logic. Control logic is provided to control how the register sets of each register group are used dependent on the operating state associated with that register group.

Data processing apparatus and method for controlling thread access of register sets when selectively operating in secure and non-secure domains

Interrupt request detection circuitry is disclosed for detecting and outputting interrupt requests to a processor. The interrupt request detection circuitry comprises: an interrupt signal input for receiving an interrupt signal; an input for receiving a signal from the processor indicating whether the processor is currently processing an interrupt; a detection circuit for detecting an interrupt request and outputting an interrupt request signal to a data processing apparatus; disabling logic for disabling at least a portion of the detection circuitry; wherein in response to detecting the processor is currently processing an interrupt; the detection circuit is configured to detect a change in value of the interrupt signal caused by assertion of the interrupt signal indicating an interrupt request and to output an interrupt request signal to output circuitry in response to detecting the interrupt signal assertion; and in response to detecting the processor is not currently processing an interrupt; the disabling logic is configured to disable at least a portion of the detection circuit; and the detection circuit with the at least a portion disabled, is configured to output the interrupt signal as the interrupt request signal to the output circuitry.

Power efficient interrupt detection

A data processing system is provided having a clock signal comparator comprising a reference input port for receiving a reference clock signal and at least a further input port for receiving respective further clock signal. Checking logic is provided within the clock signal comparator to check for a correspondence between the clock edge of the reference clock signal and a corresponding clock edge of the further clock signal within a predetermined time window. The checking logic is operable to check for the correspondence during operation of the data processing system. The clock-signal comparator can be provided on an integrated circuit or as part of the data processing apparatus having at least two different timing domains such as timing domains associated with two different instances of the same clock. Furthermore the clock-signal comparator is implemented in a hardware description language and integrated in a simulation of the operation of a data processing apparatus to detect timing errors that arise from numerical artifacts of the simulation as well as timing errors that arise from configuration and layout of the circuit elements of the data processing apparatus being simulated.

Growing community of inventors

Chatteris, United Kingdom

David Michael Gilday