Abstract: A circuit and method is provided for selectively stalling interrupt requests originating devices coupled to a multiprocessor system. The multiprocessor system includes a plurality of circuit nodes each one of which is coupled to an individual memory. An I/O bridge coupled to a first circuit node is configured to generate non-coherent memory access command packets and non-coherent interrupt command packets. The first circuit node also generates a coherent interrupt command packet in response to receiving the non-coherent interrupt command packet. The first circuit node transmits the coherent interrupt command packet to another circuit node, possibly the second circuit node. However, the transmission of the coherent interrupt command packet may be delayed. Any delay in transmission is based on a comparison of the pipe identifications of the non-coherent command packets.

Abstract: Improved transmission speed of data between computer systems is achieved by utilizing highest priority interrupts assigned to non-communication devices to control communications. In particular, the normally highest priority timer interrupts are used to poll communication buffers to determine whether data needs to be sent or received with such polling replacing the use of the interrupts typically associated with communication devices.

Abstract: The present invention provides storage system controllers and methods of controlling storage systems therewith. The controller (10) includes a main processor (12), a memory (14), a device interface (18) adapted to interface a peripheral component (28-32), such as a RAID storage device, with the storage system controller, and an operations sequencer (24). The main processor sequences a plurality of tasks to be executed to complete an operation. The operations sequencer coordinates an execution of the plurality of tasks. Methods of the invention include receiving a task status for each of the plurality of tasks that is executed, and issuing an interrupt to the main processor after all of the plurality of tasks of the operation are finished executing. In this manner, the operations sequencer offloads at least some of the main processor overhead to improve processor efficiency.

Abstract: A single microprocessor (22) hard disk drive (10) having a shared buffer memory (40) for storing sector data as well as microprocessor variables and code includes a buffer manager (38) for arbitrating requests from various channels or clients for access to the shared buffer memory. The buffer manager arranges channels including a disk data channel (32, 140), a host interface channel (50, 140), and microprocessor channels (144, 148) into a round-robin circular priority queue, with the disk data channel normally assigned the highest priority for buffer access. A state machine carries out an arbitration cycle by sequentially servicing access requests pending within the queue. The state machine senses (139) a servo interrupt (SVOINT) to elevate the priority of any pending microprocessor access requests to the shared buffer, such that the requests are serviced and cleared rapidly to allow the servo interrupt servicing routine to start sooner.

Abstract: In one embodiment, the present invention provides a storage system controller (10) having a main processor (12), a memory (14) and a device interface (18) adapted to interface with a peripheral component (28-32). The controller further includes an interrupt management scoreboard (24) adapted to receive a plurality of writes from the peripheral component(s) prior to interrupting the main processor. The main processor identifies a group of tasks to be executed, and sets up the scoreboard to await the completion of the tasks before interrupting the main processor.

Abstract: A method for managing interrupts in a microprocessor includes interrupts having a two-fold order of priority, i.e., a software priority and a hardware priority, wherein the microprocessor operates in two modes. During a first mode, the execution of an interrupt routine cannot be interrupted by the arrival of a new interrupt, even if it is a priority interrupt, unless this new interrupt is non-maskable. During a second mode, the execution of an interrupt routine is interrupted by the arrival of a priority interrupt. At the time of the execution of an interrupt, its software priority level is loaded into the state register of the microprocessor.

Abstract: A local area computer network provides distributed parallel processing. The network comprises a plurality of workstations or personal computers, each having preemptive multitasking for the interactive execution of a local task in the foreground concurrently with a remote network subtask in the background. A large compute-intensive task may be partitioned into a plurality of parallel subtasks executed simultaneously with each subtask executed in the background by a respective workstations without substantial interference with the local task being executed concurrently in the foreground. The computer time and processing power which would otherwise be wasted while waiting for slow input/output operations is instead utilized to provide a powerful parallel multiprocessor system for handling compute-intensive tasks too large for an individual workstations.

Abstract: Hardware and software techniques for interrupt detection and response in a scalable pipelined array processor environment are described. Utilizing these techniques, a sequential program execution model with interrupts can be maintained in a highly parallel scalable pipelined array processing containing multiple processing elements and distributed memories and register files. When an interrupt occurs, interface signals are provided to all PEs to support independent interrupt operations in each PE dependent upon the local PE instruction sequence prior to the interrupt. Processing/element exception interrupts are supported and low latency interrupt processing is also provided for embedded systems where real time signal processing is required. Further, a hierarchical interrupt structure is used allowing a generalized debug approach using debut interrupts and a dynamic debut monitor mechanism.

Abstract: A processing apparatus includes a network of interconnected processors comprising a plurality of signal processors for digitally processing input signals in real time to generate output signals and one or more control processors, each control processor controlling the operation of a plurality of signal processors. The processing apparatus automatically schedules control tasks in a plurality of time slices, where more than one control processor is provided for coordination between control processors, a wired-OR configuration connection can be provided to synchronise the beginning and/or end of the time slices. A control processor can change an address field of microcode instructions of a signal processor for implementing a multiplexer function. A control delay list can be provided for scheduling control task delays.

Abstract: An apparatus and method for controlling interrupts in a computer are disclosed, in which programmable software operates to control when data concerning the interrupt having highest priority is to be provided, and hardware logic operates to control how that data is provided. An interrupt vector register is included in the computer CPU. The interrupt vector register does not act like the typical register. It is not a physical register, and cannot be written to. A read to this register by the programmable software, triggers the hardware logic. Once triggered, this logic performs certain control tasks, the end result of which is returning to the programmable software, a vector corresponding to the interrupt having highest priority. The programmable software can implement various software policies, in addition to the hardware policy implemented by the hardware logic.

Abstract: A system and method for prioritizing the delivery of information transfer requests using a least-recently-serviced rotational priority technique in a data processing system having one or more requesters to supply the information transfer requests. Active requesters have currently pending information transfer requests, and non-active requesters have no currently pending information transfer requests. Transfer authorization is granted to an information transfer request associated with an active requester that is currently assigned to the highest priority level in a range of priority levels. Each of the active and non-active requesters that have a priority level less than the priority level of the active requester that was granted the transfer have their priority levels incremented, while the non-active requesters having a priority level greater than the priority level of the active requester that was granted the transfer is maintained at its current priority level.

Abstract: A processor for controlling execution of instructions stored in a main storage and interruption processing, comprises: interruption processing control device operable to accept an interruption request, analyze an accepted interruption to obtain a cause of the interruption, and generate information indicating a storage position in the main storage of a procedure for processing the cause of the interruption; specific address holding device operable to hold first address information obtained from the information generated by the interruption processing control device; and instruction execution control device operable to decide whether or not the first address information held by the specific address holding device is to be used as information indicating a storage position of an instruction to be executed and control instruction execution according to a decision result.

Abstract: A compiler comprises a using register control table by function, a using register extracting unit by function for extracting a using register and a call function name, in every function, based on the intermediate code generated from a source program, and registering the same into the using register control table by function, a using register totaling unit by function for totaling the registers used by a call function called by an interruption function, and newly registering the totaled registers in the using register control table by function as the using registers of the interruption function, and an output unit for adding saving/return codes of a using register of the interruption function to the intermediate code, with reference to the using register control table by function so to generate and supply an assembly program file.

Abstract: A method and apparatus for detecting an interrupt request in a video graphics or other system are accomplished by reading or polling a shared interrupt request flag stored in one of multiple potentially interrupting devices and determining whether a pending interrupt request exists based on a status of the shared interrupt request flag. In the event that a pending interrupt request exists, a notification of the pending interrupt request is provided to an interrupt service routine. In the event that a pending interrupt request does not exist the circuitry that is reading or polling the shared interrupt request flag delays for a polling interval and then repeats reading or polling the shared interrupt request flag and determining whether a pending interrupt request exists.

Abstract: A system and method for handling system management interrupts in a multi-processor computer is disclosed. When the computer enters system management mode, the method uses the registers of each processor to get currently executing opcode to determine what each processor was doing before the interrupt. The method may have to first translate address information to locate the actual physical location of the currently executing opcode. The registers are stored in memory and the contents of the registers can be used to determine if the current processor caused the system management interrupt. If so, then the method now knows which processor caused the interrupt and can handle the interrupt accordingly. If, however, the processor was not the one that caused the interrupt, or if another processor also caused an interrupt, the method then repeats the above steps for the next processor of the multiprocessor system.

Abstract: In an information processing apparatus, an interrupt control apparatus and method controls interrupt request inputs with respect to a processor. The interrupt control apparatus includes an interrupt flag holding circuit for holding a plurality of flags indicative of interrupt factors with respect to the respective interrupt request inputs and also holds a plurality of interrupt levels representative of priority orders of the interrupt request inputs. An interrupt level judging circuit judges an interrupt level having a top priority and also outputs an interrupt request to the processor. An interrupt vector generating circuit generates an interrupt vector in response to the held interrupt factor and an interrupt vector outputting circuit outputs the held interrupt vector to the processor.

Abstract: A method and apparatus for managing interrupt requests from devices on a subordinate bus is disclosed. An interrupt request storage area is provided on the bridge device to allow the bridge device to log and track interrupt requests. Once an interrupt request from an interrupting device is logged, all previous transactions from the interrupting device is allowed to complete while no further transactions from the interrupting device is allowed. All other devices operates normally during this time. Once the interrupt request is serviced, the interrupting device is allowed to resume normal operation. By providing a storage area to store the interrupt requests from devices on a subordinate bus, the unprocessed transactions in the bridge device and transactions from all other devices can be processed in an orderly manner.

Abstract: A peripheral device connecting system with priority arbitration includes a connection matrix connected to a plurality of peripheral devices capable of transmitting a signal to be arbitrated, e.g., an interrupt enable signal. The connection matrix includes first and second connection matrices connected to each other through a plurality of logic gates having a progressive number of inputs for transmitting in parallel a plurality of signals to be arbitrated. A connection matrix for a microcontroller-emulating chip includes a peripheral device connecting system with priority arbitration.

Abstract: A computer program or a computer process is provided by replacing a native computer instruction with a trapping computer instruction which is the size of the native computer instruction and which, when executed, causes a trap to the kernel. A trap handler in the kernel determines that the inserted trapping computer instruction caused the trap and transfers control to a user trap handler. The user trap handler maps the trap site to a patch of computer instructions. When the trapping computer instruction is executed, the trap handler transfers control from the kernel to the user trap handler which in turn transfers control to the patch. Native computer instructions in sufficient proximity to corresponding patches of computer instructions may be replaced with branching computer instructions of the size of the native computer instruction and which transfer control to those corresponding patches.

Abstract: In a storage target device controller capable of managing multiple command contexts, methods and associated apparatus are provided for automatically managing the plurality of contexts using a state machine model. The state machine model is operable on a target device controller having an active context register set for processing of the presently active transfer on the host channel and an inactive context register set for storing an inactive context. The active context register set and inactive context register set are rapidly and automatically swapped by operation of the state machine model to resume or start processing of an inactive context. Additional inactive contexts are stored in a buffer memory associated with the target device controller. The inactive context register set is automatically stored into a selected one of the additional inactive contexts or loaded from a selected one of the additional inactive contexts by operation of the state machine model of the present invention.

Abstract: Each node of multinode computer system includes an interrupt controller, a pair of send and receive queues, and a state machine for communicating interrupts between nodes. The communication among the interrupt controller, the state machine, and the queues is coordinated by a queue manager. For sending an interrupt, the interrupt controller accepts an interrupt placed on a bus within the node and intended for another node and stores it in the send queue. The controller then notifies the interrupt source that the interrupt has been accepted before it is transmitted to other node. The interrupt has a first form suitable for transmission on the bus. A state machine within the node takes the interrupt from the send queue and puts the interrupt into a second form suitable for transmission across a network connecting the multiple nodes.

Abstract: A communication channel is operated in a mixed master/slave subscriber environment by a dynamical closing/opening operation. In particular, a separate handshaking between each subscriber and a central communication module is undertaken. The latter first asserts a first halt command to every master for assuming a first halt state. Upon finding universal prevalence of the first halt state a second halt command is asserted to every slave for assuming a second halt state. Upon detecting universal prevalence of the second halt state a “communications switched off” mode is provided. For resuming, a reverse sequence is executed.

Abstract: Method and apparatus for performing access censorship in a data processing system (10). In one embodiment, a digital data processing system (10) has a sub-system (34) that can be protected against intrusions, yet is still accessible and/or alterable under certain defined conditions. In a non-volatile storage portion (48) of the data processing system (10), censorship information is stored to enable an access control mechanism. Access control information (42) to selectively disable the access control mechanism is programmably generated. Additional access control information (44) can be employed to reprogram a data processing system (10) containing access protected data in a secure mode.

Abstract: Task control via a multi-task or real time operating system that reduces the size of a RAM in which a stack region for processing the tasks, as well as an interrupt processing function, is set. An interrupt for interrupting any of a plurality of individual tasks having set priorities at a higher priority than the set priorities of the individual tasks is set. Thereafter, a stack region is set for processing the individual tasks and the interrupt in a writable and readable memory. The size of the stack region is then set to a size necessary for processing the individual tasks and in accordance with a task number, while a separate stack region is set for the interrupt.

Abstract: An interrupt load distribution system for a shared bus type multiprocessor system includes a processor statistical information table for storing processor statistical information consisting of processor activity ratios under the use by the operating system, processor activity ratios under the use by processes executing under a processor bind, and number of processes requesting a bind from each processor, an interrupt schedule information table for storing interrupt schedule information, an interrupt scheduler for referring to said two tables at fixed time intervals and re-scheduling interrupt load distribution as necessary to achieve appropriate distribution, and an I/O control part for notifying the designated processor of an interrupt request by reflecting a re-schedule created by the interrupt scheduler.

Abstract: In one embodiment, the invention includes an apparatus, such as a bridge, for use with a computer system having a processor bus. The apparatus includes decode logic to receive through the processor bus a task priority update transaction including data representative of a task priority designation of a processor of the computer system, and to provide a signal responsive thereto. The apparatus also includes remote priority capture logic to receive the signal responsive to the task priority update transaction and update contents of the remote priority capture logic in response thereto. In another embodiment, the invention includes an apparatus for use with a computer system having a processor bus. The apparatus includes decode logic to receive through the processor bus an end-of-interrupt (EOI) transactions and to provide an EOI signal responsive thereto.

Abstract: A computer system processes system management interrupt (SMI) requests from plural system management (SM) requesters. Different SM requesters are provided with different priority levels such that high priority system management interrupts can be serviced without waiting for lower priority system management interrupts to be serviced completely. In particular, the system executes a first SMI handler routine in response to receiving a first SMI from a first SM requester. In response to receiving a second SMI asserted by a second SM requester, the system determines whether the second SMI request has been assigned a higher priority than the first SMI request. If so, then the system interrupts executing the first SMI handler routine and executes a second SMI handler routine corresponding to the second SMI request. Otherwise, the system completes executing the first SMI handler routine and then executes the second SMI handler routine.

Abstract: In a method for switching between multiple system hosts (154,164,174,184) on a CompactPCI bus (110,120), a hot swap controller (166,186) provides to a special arbiter (820) a high priority request signal and the special arbiter (820) provides to the hot swap controller a grant signal only when the CompactPCI bus is idle. The hot swap controller (166,186) provides to the special arbiter (820) a float signal causing the special arbiter (820) to disable the system host signals, which include one or more grant signals for granting bus access to devices on the CompactPCI bus (110,120), one or more reset signals for resetting the devices, one or more interrupts and one or more clock signals provided to devices. The hot swap controller (166,186) transfers control of the CompactPCI bus (110,120) to a standby system host 154,164,174,184).

Abstract: An interrupt messaging scheme for a multiprocessing computer system where a dedicated bus to carry interrupt messages within the multiprocessing system is eliminated. Instead, an interconnect structure using a plurality of high-speed dual-unidirectional links to interconnect processing nodes, I/O devices or I/O bridges in the system is implemented. Interrupt messages are transferred as discrete binary packets over point-to-point unidirectional links. Various interrupt requests are transferred through a predetermined set of discrete interrupt message packets. Interrupt message initiators—an I/O interrupt controller or a local interrupt controller (in case of an inter-processor interrupt)—may be configured to generate appropriate interrupt message packets upon receiving an interrupt request. A suitable routing algorithm may be employed to route various interrupt messages within the system.

Abstract: In a method and system for use in connection with performing a processor-to-bus cycle in a multi-processor computer system, the processor-to-bus cycle is interrupted before completion and an operation to save data in memory is performed. Thereafter, the interrupted processor-to-bus cycle is resumed.

Abstract: A non-uniform memory access (NUMA) computer system includes at least two nodes coupled by a node interconnect, where at least one of the nodes includes a processor for servicing interrupts. The nodes are partitioned into external interrupt domains so that an external interrupt is always presented to a processor within the external interrupt domain in which the interrupt occurs. Although each external interrupt domain typically includes only a single node, interrupt channeling or interrupt funneling may be implemented to route external interrupts across node boundaries for presentation to a processor. Once presented to a processor, interrupt handling software may then execute on any processor to service the external interrupt. Servicing external interrupts is expedited by reducing the size of the interrupt handler polling chain as compared to prior art methods.

Abstract: A computer system processes system management interrupt (SMI) requests from plural system management (SM) requesters. Different SM requesters are provided with different priority levels such that high priority system management interrupts can be serviced without waiting for lower priority system management interrupts to be serviced completely. In particular, the method includes executing a first SMI handler routine in response to receiving a first SMI from a first SM requester. In response to receiving a second SMI asserted by a second SM requester, the method determines whether the second SMI request has been assigned a higher priority than the first SMI request. If so, then the method interrupts executing the first SMI handler routine and executes a second SMI handler routine corresponding to the second SMI request. Otherwise, the method completes executing the first SMI handler routine and then executes the second SMI handler routine.

Abstract: A method and apparatus for reducing interrupt density in a computer system. One or more interrupt events received at a first device are stored in a memory and an interrupt is issued from the first device to a second device attached to the first device upon an occurrence of a first predefined event, wherein the second device retrieves the stored interrupt events from the memory and processes the retrieved interrupt events in response to the issued interrupt. Thereafter, an interrupt is issued for every interrupt event from the first device to the second device after the occurrence of the first predefined event until an occurrence of a second predefined event. After the occurrence of the second predefined event, the interrupt events received at a first device are again stored in the memory without issuing an interrupt from the first device to the second device. Finally, an interrupt is issued from the first device to the second device upon another occurrence of the first predefined event.

Abstract: A network adaptor that generates interrupts to a host system when data is received from the network or downloaded from system memory for transmittal over the network. The adaptor generates interrupts after a delay determined by an interrupt deferral mechanism, which includes one or more timers and/or one or more counters. Interrupts are generated, for example, after a predetermined time has elapsed after a DMA completion or after a certain number of packets are counted.

Abstract: A method for returning from an interrupting context to an interrupted context in a processor is disclosed. The processor executes a programmed flow of instructions. The processor includes a register stack (RS) and a register stack engine (RSE) to exchange information between the RS and the storage area. The method includes the following steps: (a.) A first pointer (PTR) is generated. The pointer (PTR) points to a location in the storage area where dirty registers (previously unsaved) of an interrupted context are stored; (b.) It is determined whether a mathematical relation is valid between the first pointer and the second pointer (BSPLOAD) to a location in the storage area from where the RSE is configured to load dirty register values into the RS; (c) The second pointer is caused to point to a next location in the storage area if the relation is valid; and (d) A register of the RS is loaded with a content of the next location in the storage area until the mathematical relation becomes invalid.

Abstract: A computer implemented method for switching from an interrupted context to an interrupting context in a processor is provided. The processor includes a register stack (RS) that has first and second portions. The processor includes a register stack engine (RSE) that exchanges information, in one of instruction execution dependent and independent modes between the second portion and a storage area. The method includes the following steps: a state of the RSE of the interrupted context is preserved; a COVER instruction is issued; a first (BSPSTORE) pointer is preserved. The first pointer points to a location in the storage area, of the interrupted context, where a next register of the second portion is to be written; first pointer is written with a value corresponding to the interrupting context; and a second pointer (BSP) is preserved. The new first and second pointers in the interrupting context define the storage area of RS values associated with the interrupted context.

Abstract: A system and method is provided for processing interrupt requests. The method is accomplished by detecting when an interrupt request is being stored in a storage location, examining the storage location storing the interrupt request, prioritizing the interrupt request when more than one interrupt request is stored in the storage location to determine an interrupt request processing order, clearing the interrupt request in the storage location that is to be processed, and processing the interrupt request. The system comprises a first storage location for storing an interrupt request, a second storage location for storing an interrupt handler program with encoded statements for examining the first storage location, prioritizing the interrupt request that is to be processed if more than one interrupt request is stored in said first storage location, clearing the interrupt request that is to be processed, and processing the interrupt request.

Abstract: An apparatus and method minimizes processing resource of a host system during service of interrupts generated closely in time by at least one peripheral device. The present invention determines, before the end of a prior interrupt service routine for a prior interrupt, a predicted interrupt time point when a subsequent interrupt will be generated by the at least one peripheral device. The host system operates in a polling mode if the predicted interrupt time point is before a predetermined time period after the end of the prior interrupt service routine. Thus, the host system avoids the processing resources needed for context switching time when the subsequent interrupt is generated closely in time from the prior interrupt. The host system operates in an interrupt mode if the predicted interrupt time point is after the predetermined time period after the end of the prior interrupt service routine.

Abstract: A multithreaded program includes sequences of events wherein each sequence is associated with one of a plurality of execution threads. In a record mode, the software tool of the present invention records a run-time representation of the program by distinguishing critical events from non-critical events of the program and identifying the execution order of such critical events. Groups of critical events are generated wherein, for each group G.sub.i, critical events belonging to the group G.sub.i belong to a common execution thread, critical events belonging to the group G.sub.i are consecutive, and only non-critical events occur between any two consecutive critical events in the group G.sub.i. In addition, the groups are ordered and no two adjacent groups include critical events that belong to a common execution thread. For each execution thread, a logical thread schedule is generated that identifies a sequence of said groups associated with the execution thread.

Abstract: An interrupt control system is provided in a computer having a processor, a PCI bus, an ISA bus, and a serial transfer line. An interrupt controller outputs interrupt requests to the processor according to the priority levels of signals received from the PCI bus and the ISA bus. Interrupt signals supplied to the interrupt controller from the PCI bus and ISA bus are mapped to a level appropriate for the interrupt controller.

Abstract: A software configurable technique for prioritizing and masking interrupts in a microprocessor-based system. Contents of a first plurality of registers map each of a plurality of interrupts to an appropriate one of a second plurality of registers and indicate which interrupts are masked. The second plurality of registers are arranged in a predetermined priority and each contains the starting address of an appropriate interrupt service routine for the corresponding interrupt. The interrupt signals are mapped to the outputs of a plurality of logical "OR" gates according to the contents of the first plurality of registers by a plurality of de-multiplexers coupled to the inputs of the plurality of logical "OR" gates. Each logical "OR" gate corresponds to one of the second plurality of registers.

Abstract: An interrupt controller comprises a plurality of interrupt handling elements that are given different identification numbers for identification to which priorities are assigned. A first priority encoder accepts a plurality of level signals which are given different level numbers respectively representing the priorities assigned to the identification numbers, and then encodes the level number assigned to the highest-priority level signal included among all level signals at a low potential so as to generate an interrupt level number representing the encoded level number.

Abstract: An interrupt program selection system which is provided with a central processing unit executing various types of control programs stored in a storage unit and which accepts an interrupt processing request from an external unit and selects from the storage unit an interrupt program corresponding to the accepted request comprises an interrupt request controller, a conversion table, and a jump code generating module. The interrupt request controller selects a highest-priority processing request from a plurality of interrupt processing requests. The conversion table contains start addresses of a plurality of interrupt programs corresponding to a plurality of interrupt processing requests. The jump code generating module generates a jump code which may be executed directly by the central processing unit as an instruction based on the start address of the interrupt program corresponding to the accepted interrupt processing request, and places the generated code in a memory space in the storage unit.

Abstract: An input/output bus bridge and command queuing system includes an external interrupt router for receiving interrupt commands from bus unit controllers (BUCs) and responds with end of interrupt (EOI), interrupt return (INR) and interrupt reissue (IRR) commands. The interrupt router includes a first command queue for ordering EOI commands and a second command queue for ordering INR and IRR commands. A first in first out (FIFO) command queue orders bus memory mapped input output (MMIO) commands. The EOI commands are directed from the first command queue to the input of the FIFO command queue. The EOI commands and the MMIO commands are directed from the command queue to an input output bus and the INR and IRR commands are directed from the second command queue to the input output bus. In this way, strict ordering of EOI commands relative to MMIO accesses is maintained while simultaneously allowing INR and IRR commands to bypass enqueued MMIO accesses.

Abstract: An information handling system includes one or more processing units, a data management unit, connected to the processor data bus, to a memory system, and to an I/O bus, an address management unit, connected to the processor address bus, to the memory system, and to an I/O bus. Data management unit also includes interrupt routing logic which snoops interrupt packets, stores the information in registers, and generates a signal indicating whether a particular interrupt was accepted or rejected. If the interrupt logic has a higher priority interrupt pending, the current interrupt packet will be returned to the requesting device using the interrupt return transaction, and the requesting device will accept the return transaction by decoding the bus unit ID field in the packet. The interrupt will be requeued and held in a pending status until an interrupt reissue transaction is transmitted by the interrupt routing logic and received by the interrupting I/O controller.

Abstract: An interrupt service table pointer (ISTP) facilitates fast branching to interrupt service routines. An interrupt service table base (ISTB) field establishes a base address at which one or more routines reside in memory. A highest priority enabled interrupt (HPEINT) field identifies an interrupt to service. The concatenation of the ISTB, the HPEINT, and one or more least significant zeros points to the first instruction of a group of instructions which service a specific interrupt. The ISTB is user programmable. The HPEINT is automatically calculated each cycle by the data processor incorporating the ISTP.

Abstract: A microcontroller including a streamlined pipeline processor provides a predictable time period for executing a set of instructions including branch instructions. The microcontroller has a program counter, branch stack and pipeline stages that can be loaded in a single cycle, and allows only the execution stage of the pipeline to alter the CPU state. Thus, the instructions in stages preceding the execution stage can be annulled, and the necessary registers can be updated in the first cycle upon determination of a branch instruction. In subsequent cycles, instructions in the branch routine will flow through the pipeline, one stage per cycle. Thus, a fixed period for responding to a branch instruction is provided. A fixed period for responding to an interrupt is also provided, as is a selectable interrupt schedule for predictable instruction execution in a multi-tasking operation.

Abstract: A network device such as an Asynchronous Transfer Method (ATM) device with a high level interrupt which begins processing a packet and transfers process control to a lower level software interrupt which completes the packet processing. Prior to the transfer of process control, the hardware interrupt generates a put information for the packet which is then retrieved and utilized by the software interrupt to process the packet. A unique generation number is assigned to each data stream generated for the packet. The generation number associated with a given packet's put information is compared to the generation number of a data stream to which the packet is destined to. If the generation numbers are equal, it is assumed that the data stream to which the packet is destined to has not been changed and the packet is forwarded to the data stream for further processing.

Abstract: A protection circuit for the prevention of program interruptions of electrical equipment controlled on the basis of program step clocks, by too frequent occurrences of non-maskable interrupt signals. This protection circuit comprises a controllable interrupt signal passage circuit which, depending on an output signal of a control signal source, can be controlled to a state permitting the passage of the non-maskable interrupt signal or to a state blocking said signal. The control signal source comprises a clock counter with overflow resetting function, by means of which program step clock pulses can be counted starting from a predetermined initial counting value until a predetermined overflow counting value is reached. The control signal source comprises furthermore an interrupt signal counter the counting value of which can be increased by each non-maskable interrupt event and decreased each time the overflow counting value of the clock counter is reached.

Abstract: A multiprocessor architectural definition provides that a program executing on a first processor interrupts a second processor by executing a software interrupt instruction. The software interrupt instruction includes an argument field for passing information from a program requesting the software interrupt. The argument, along with the opcode, is saved in a register designated for holding the argument. The information communicated via the argument is used in one embodiment to indicate a cause of the interrupt. In an embodiment, the information communicated via the argument designates an interrupt service routine to be activated in the interrupted processor.