Arm Limited

Peter James Aldworth

Daren Croxford

Andrew David Tune

David Hennah Mansell

Simon Charles Watt

Lionel Belnet

Paul Matthew Carpenter

Andrew Benson

A data processing system is provided with a memory controller () converting memory addresses () into selecting signals () for a memory device (). The mapping between memory addresses and selecting signals is provided by mapping logic () within the memory device. The configuration of the mapping logic, also known as a mapping scheme, is defined by data stored in mapping specifying data storage (), which may be altered by operating system software or application software () running on the system. Altering this configuration may be as a result of signals received from a monitoring unit () which monitors the efficiency with which the current mapping scheme is accessing data stored in the memory device. More than one mapping scheme may be used within a single memory device.

Memory controller address mapping scheme

A data processor includes a cache memory having a plurality of cache rows each row storing a cache line of data values, a memory management unit responsive to a page table entry to control access to a corresponding group of memory addresses forming a memory page, and a cache controller coupled to said cache memory and responsive to a cache miss to trigger a line fill operation to store data values into a cache row. The cache controller is responsive to a cache line size specifier associated with at least one page table entry to vary the number of data values within a cache line fetched in a line fill operation in dependence upon said cache line size specifier. Controlling cache line size on a page basis is more efficient than controlling cache line size on a cache row or virtual address basis.

Cache memory

A method, an interconnect and a system for processing data is disclosed. The method comprises the steps of: a) receiving a request to perform a data transaction between a master unit and a slave unit, b) receiving an indication of a quality of service requirement associated with said data transaction; c) determining an interconnect quality of service level achievable when transmitting said data transaction over the interconnect logic having regard to any other pending data transactions which are yet to be issued; d) determining a slave quality of service level achievable when responding to said data transaction once received by said slave unit from said interconnect logic; and e) determining whether the combined interconnect quality of service level and the slave quality of service level fails to achieve the quality of service requirement and, if so, reordering the pending data transactions to enable the quality of service requirement of each data transaction to be achieved. Hence, arbitration between data transactions occurs prior to those transactions being provided to the interconnect. It will be appreciated that this enables pending data transactions to be systematically reordered and the quality of service level for each of these reordered data transactions to be accurately calculated to ensure that the quality of service requirement for each of those data transactions is achieved. Accordingly, this enables all aspects of quality of service to be budgeted together and true end-to-end quality of service may be determined for each data transaction.

Arbitration method reordering transactions to ensure quality of service specified by each transaction

A data processing apparatus and method are provided for controlling access to a slave device, the slave device having an address range associated therewith. The apparatus comprises control storage programmable to define a partition identifying a secure region and a non-secure region in the address range, with the data processing apparatus supporting a plurality of modes of operation including a secure mode, and the control storage being programmable only by software executing in the secure mode. A master device is arranged to issue an access request onto a bus, the access request identifying a sequence of addresses within the address range and including a control signal indicating whether the access request is a secure access request or a non-secure access request. The secure region is only accessible by a secure access request. Further, access control logic is provided which is associated with the slave device, the access control logic being operable to receive the access request from the bus and an indication of the partition from the control storage and, if the access request is a non-secure access request, to prevent access to the secure region.

Access control in a data processing apparatus

A data processing system using a main processorand a coprocessorprovides coprocessor load instructions (USALD) for loading a variable number of data values dependent upon alignment into the coprocessorand also specifying data processing operations to be performed upon operands within those loaded data words to generate result data words. The specified coprocessor processing operations may be a sum of absolute differences calculation for a row of pixel byte values. The result of this may be accumulated within an accumulate register. A coprocessor memoryis provided within the coprocessorto provide local storage of frequently used operand values for the coprocessor

Data processing using a coprocessor

The present invention relates to an interface mechanism and particularly to an interface mechanism for interfacing a real-time clock operating at a first frequency with a data processing circuit operating at a second frequency. The interface mechanism comprises a first input for receiving a relative real-time clock value from the real-time clock, and a second input for receiving an update value from the data processing circuit specifying a desired value for the real-time clock. Update logic is also provided for producing an absolute real-time clock value, the update logic being arranged in response to receipt of the update value to generate an offset value derived from the relative real-time clock value and the update value, the offset value then being applied to the relative real-time clock value to produce an updated absolute real-time clock value. The updated absolute real-time clock value is then output from the interface mechanism. This enables the update of the real-time clock to be performed very efficiently, without the need to perform any of the update procedure in the slow frequency domain of the real-time clock.

Interface mechanism and method for interfacing a real-time clock with a data processing circuit

The present invention provides a data processing circuit and method for performing arithmetic processing on data signals input to the circuit, comprising: a plurality of input terminals for receiving a plurality of data signals to be processed; a plurality of interconnected arithmetic processing units, one corresponding to each input terminal, for processing the data signals received at the corresponding input terminal; and a selector for routing the data signals at said input terminals to the corresponding arithmetic processing units in a first mode of operation, or for routing a selected one of said data signals to said plurality of arithmetic processing units in a second mode of operation; whereby, in said first mode of operation, data signals arriving at said input terminals are processed in parallel by said corresponding arithmetic processing units, and, in said second mode of operation, at any point in time, one of said data signals is processed by said plurality of arithmetic processing units. By this approach, the data processing circuit is provided with two modes of operation, the first mode of operation corresponding to a fast, reduced precision mode of operation, whilst the second mode of operation corresponds to a slower but higher precision mode of operation. The same hardware is reused for both modes of operation, thereby reducing the hardware requirements and so enabling the circuit to be relatively small.

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Cambridge, United Kingdom

Peter James Aldworth