Abstract: A system is provided in which a first circuit is protected by security features provided by a second circuit. The first circuit comprises a processor which retrieves content from a memory. Initially, the contents of the memory are authenticated using security features of the second circuit to check that the processor is accessing authenticated content. To maintain security during use, the second circuit checks that the processor is accessing content from valid regions of the memory, being those that have been authenticated, and re-checks the authenticity of the content of the valid regions of memory. The combination of checking that the processor is accessing from valid regions of the memory and authenticating the content stored in the valid regions maximizes the security of the system. If any of the checking or authentication steps fail then operation of the system is impaired. The first circuit is thus protected by security features provided by the second circuit.

Abstract: A processing system which comprises means for storing a plurality of items defining a queue, pointer means having a first pointer and a second pointer associated with the beginning of said queue and a second pointer associated with the back of said queue; at least one writer for adding items to said queue; at least one reader for deleting items from said queue; and means for updating said second pointer when said at least one writer adds an item to said queue, said second pointer being updated by a swap operation.

Abstract: A computer system is formed by two interconnected chips each having on chip a CPU connected to a module by an on chip and data path, for distributing event request packets, the paths of the two chips being connected through external ports so that addresses on each of the paths form part of a common address space addressable from either chip.

Abstract: There is disclosed a computer system including a microprocessor on a single integrated circuit chip comprising an on-chip CPU and a communication bus providing a parallel communication path between the CPU and at least one of the module with logic circuitry. The integrated circuit device further comprises an external communication port connected to the bus, having an internal parallel format for connection to the bus. The external port further has an external signal having an external format less parallel than the internal format. Translation circuitry is provided to effect conversion between said internal and external formats. There is also disclosed a method of operating such a computer system.

Abstract: A computer system comprises on-chip a CPU with at least one different module, both having circuitry to generate two types of address request packets, one being a control command packet to which a destination device must respond on receipt and the other type being an interrupt request with a priority indicator for a selective response by the destination device.

Abstract: A computer system provides on chip at least one CPU connected to another module by an address and data path, the module generating interrupt request packets with a destination address, the CPU decoding the packet, identifying a priority for the interrupt request and selectively responding to the request.

Abstract: A processing system which comprises means for storing a plurality of items defining a queue, pointer means having a first pointer and a second pointer associated with the beginning of said queue and a second pointer associated with the back of said queue; at least one writer for adding items to said queue; at least one reader for deleting items from said queue; and means for updating said second pointer when said at least one writer adds an item to said queue, said second pointer being updated by a swap operation.

Abstract: An adapter device for assisting debugging of a microprocessor on a single integrated circuit chip, the integrated circuit chip comprising an on-chip CPU with a plurality of registers, a communication bus providing a parallel communication path between the CPU and a first memory local to the CPU and an external communication port connected to the said bus on the integrated circuit chip, the communication port having an internal connection to the said bus of an internal parallel signal format and an external connection to the adapter unit of a first external format less parallel than the said internal format; the adapter device comprising a first communication unit for connection to the communication port with the first external format; a second communication unit for connection to an external computer device with a second external format having a higher latency than the first external format; a second memory local to the adapter device; and a processing unit local to the adapter device and operable: (a) in a f

Abstract: An adapter device for assisting debugging of a microprocessor on a single integrated circuit chip, the integrated circuit chip comprising an on-chip CPU with a plurality of registers, a communication bus providing a parallel communication path between the CPU and a first memory local to the CPU and an external communication port connected to the said bus on the integrated circuit chip, the communication port having an internal connection to the said bus of an internal parallel signal format and an external connection to the adapter unit of a first external format less parallel than the said internal format; the adapter device comprising a first communication unit for connection to the communication port with the first external format; a second communication unit for connection to an external computer device with a second external format having a higher latency than the first external format; a second memory local to the adapter device; and a processing unit local to the adapter device and operable: (a) in a f

Abstract: The transmission of interrupts is described where the interrupt is represented at a peripheral device by the electrical level of a conductor but where it is conveyed to a receiving module by way of a message packet routed along a routing path. According to one aspect, the message packet includes the identification of the peripheral device which generated the interrupt and the receiving module acts on the message packet to implement an interrupt handling routine depending on the identification of the peripheral device. According to another aspect, the message packet includes a transaction identifier which uniquely identifies one of a series of interrupts, and the receiving module generates a response packet containing that transaction identifier thereby allowing the peripheral device to monitor whether or not its interrupts have been treated properly.

Abstract: A single integrated circuit chip connected to an external computer device. The chip includes a CPU with registers, a bus for addressing devices assigned to a memory address space of the CPU and providing a parallel path between the CPU and a first memory local to the CPU, an address memory for storing addresses assigned to the devices, and an external port connected to the bus. The port includes an internal parallel signal format connection to the bus and a less parallel external connection to the external computer device. The port forms part of the memory address space of the CPU. The external computer device includes a second memory local to the external computer device and accessible by the CPU through the port. Address diversion means are provided for reconfiguring the memory address space of the CPU to assign to the port memory addresses of another one of the devices.

Abstract: A computer system includes on-chip a CPU with an addressable module and a memory interface, the module having packet generating circuitry for event request or control packets, the CPU being operable to generate event request packets, memory access packets or control packets having a common format with packets generated by said module.

Abstract: A system and method for communication between a CPU and on-chip modules in an integrated circuit and off-chip devices is disclosed. A path on the integrated circuit allows for packet traffic to flow between the CPU and modules. In some embodiments the path is a data bus. Various types of packets are used, but each include a destination indicator to indicate the required destination device connected to the path. Data transfer packets are used for memory access operations. Normal event packets form prioritized interrupts wherein the recipient CPU or module respond to the event packet depending on relative priorities associated with other packets sent to the recipient device. Special event packets form command control signals that must be acted on by the recipient device when the special event packet is received.

Abstract: There is disclosed a computer system comprising a microprocessor on a single integrated circuit chip connected to an external computer device. The chip has a CPU and a communication bus providing a parallel communication path between the CPU and the first local memory. The chip further comprises an external communication port connected to the bus, the external computer device being connected to an external communication port and having a second memory. The port has an internal connection of an internal parallel signal format and an external parallel signal format and an external connection of an external format less parallel than the internal format. The second memory is accessible by the CPU through the port, the port forming part of the memory address space of the CPU from which instructions may be fetched. The port may be addressed by execution of an instruction by said CPU. There is also discloses a method of operating such a computer system.

Abstract: A computer system includes an address and data path interconnecting an on-chip CPU with a module and an external communication port, event request packets being generated by the CPU and the module and memory access packets being generated by the CPU, each packet having a destination address and being distributed in parallel format on-chip with a reduction to a more serial format for off-chip communication.

Abstract: A computer system that includes a microprocessor, and at least one other device on a single integrated circuit chip that can be connected to an external computer device. The integrated circuit chip includes: an on-chip CPU having a plurality of registers, a communication bus for providing a parallel communication path between the CPU and a first memory local to the CPU, and an external communication port connected to the communication bus. The port [having] has an internal connection to the communication bus with an internal parallel signal format and an external connection to the external computer device with an external format less parallel than the internal parallel signal format.

Abstract: There is disclosed a computer system including a microprocessor on an integrated circuit chip comprising an on-chip CPU and a debugging port connected to a communication bus on the integrated circuit and to an external debugging computer device. The external debugging device is operable to transmit control signals through the debugging port: a) to stop execution by the CPU of instructions obtained from a first on-chip memory; b) to provide from a second memory associated with the external debugging computer device a debugging routine to be executed by the CPU; and c) to restart operation of the CPU after the routine with execution of instructions from an address determined by the external debugging device. The on-chip CPU is operable with code in the first memory which is independent of the debugging routine. A method of operating such a computer system with an external debugging device is also disclosed.

Abstract: A cache coherency mechanism for a computer system having a plurality of processors, each for executing a sequence of instructions, at least one of the processors having a cache memory associated therewith. The computer system includes a memory that provides an address space where data items are stored for use by all of the processors. A behavior store holds in association with an address of each item, a cache behavior identifying the cacheable behavior of the item, the cacheable behaviors including a software coherent behavior and an automatically coherent behavior. When a cache coherency operation is instigated by a cache coherency instruction, the operation is effected dependent on the cacheable behavior associated with the specified address of the item. Methods for modifying the coherency status of a cache are also described.

Abstract: A bus arbitration system is described which includes an arbitrator for controlling accesses to a memory bus by a plurality of memory users in response to requests made by those memory users. Each memory user reads the address if a current access to memory and generates a same-address-set signal when the address of the last access by that memory user lies in the same set as the address of the current access. The arbitrator holds for each memory user a predetermined number of accesses which are permitted by that memory user during an access span, and, responsive to a request, grants up to that predetermined number of accesses provided that the same-address-set signal is asserted.

Abstract: There is disclosed a computer,system including a microprocessor on an integrated circuit chip comprising an on-chip CPU and a communication bus. The communication bus provides a parallel communication path between the CPU and the first memory local to the CPU. An external port of the integrated circuit is connected to said bus and to an external computer device having a second memory. The external computer device is operable to transmit control signals through the port: a) to suspend execution by the CPU of instructions obtained from the first memory; b) to provide from the second memory boot code to be executed by the CPU; and c) to restart operation of the CPU using said boot code. There is also disclosed a method of operating such a computer system.