Abstract: A communication device configured to communicate according to a data protocol in which data is carried in packets over a serial data link and the communication device is arranged: to form packets for transmission over the link in such a way that every packet commences with a first bit value; and between transmitting successive packets to continuously transmit a second bit value opposite to the first bit value over the link.

Abstract: A method of tracing transactions on an integrated circuit chip. The method comprises, for each transaction: extracting the transaction from interconnect circuitry of the integrated circuit chip, the transaction comprising an address signal and a data signal; applying a filtering condition to the address signal; only if the address signal does not fail the filtering condition, storing the address signal in an address trace buffer; storing the data signal in a data trace buffer; applying a triggering condition to the stored transaction; and outputting the stored transaction if the stored transaction matches the triggering condition.

Abstract: A method of profiling transactions on an integrated circuit chip. The method comprises, for each transaction: extracting the transaction from interconnect circuitry of the integrated circuit chip; and filtering the transaction at a filtering circuit to determine which passband a parameter of the transaction lies within; sending an increment signal to a counter of a bank of counters, the counter having a counter value indicative of a number of transactions having the parameter lying within the passband; and outputting the counter values of the bank of counters.

Abstract: An integrated circuit chip comprising system circuitry and debugging circuitry. The system circuitry comprises a peripheral circuit. The debugging circuitry comprises a debug unit and a debug adapter. The debug unit is connected to the peripheral circuit. The debug adapter interfaces between the debug unit and a debug controller. The debug adapter is configured to receive a sequence of debug commands from the debug controller, each debug command instructing the debug unit to perform an action other than responding to a poll. In respect of each debug command, the debug adapter sends the debug command to the debug unit, and polls the debug unit to query whether the debug unit has performed the action instructed in that debug command.

Abstract: A method of reconfiguring a current debug configuration of a debug unit connected to a peripheral circuit on an integrated circuit chip. The method comprises the debug unit collecting debug data of the peripheral circuit and outputting the debug data in a message stream. The debug unit receives a debug reconfiguration command. The debug unit transmits an indication of the current debug configuration, then reconfigures the current debug configuration to a new debug configuration in accordance with the debug reconfiguration command, then transmits an indication of the new debug configuration. The indication of the current debug configuration and the indication of the new debug configuration are transmitted adjacent to the debug data in the message stream.

Abstract: Roughly described, a method of restricting access of a debug controller to debug architecture on an integrated circuit chip, the debug architecture comprising an access controller, a plurality of peripheral circuits, and a shared hub, the shared hub being accessible by the access controller and the plurality of peripheral circuits, the method comprising: at the access controller, authenticating the debug controller; at the access controller, following authentication, assigning to the debug controller a set of access rights, the set of access rights granting the debug controller partial access to the debug architecture; and after assigning the set of access rights, allowing the debug controller access to the debug architecture as allowed by the set of access rights.

Abstract: An integrated circuit chip device comprising: system circuitry; debugging circuitry configured to debug the system circuitry, the debugging circuitry being segmented into zones; wherein the debugging circuitry comprises an interconnect fabric configured to route debug messages through a zone from a zone entry node of the interconnect fabric to a zone exit node of the interconnect fabric; and wherein the debugging circuitry is configured to, on receiving a debug message at a zone entry node that is shorter than a specified length, modify the debug message to form a modified debug message by increasing the length of the debug message to the specified length.

Abstract: A method of functionality testing system circuitry on an integrated circuit chip, the system circuitry comprising a plurality of sub-circuits and the integrated circuit chip further comprising debugging circuitry, the debugging circuitry comprising variability circuitry. The method comprises: at the system circuitry, performing a function by the sub-circuits performing concurrent actions; at the variability circuitry, altering relative timing of the concurrent actions so as to increase the likelihood of one or more errors in the system circuitry's performance of the function; and at the debugging circuitry, recording one or more errors in the system circuitry's performance of the function.

Abstract: Roughly described, a method of powering down a portion of an integrated circuit chip, the portion of the integrated circuit chip comprising a plurality of peripheral circuits, each peripheral circuit being connected to a respective debug unit, the method comprising: prior to power down, extracting from each debug unit configuration information of that debug unit; storing the configuration information of the debug units in a memory on the integrated circuit chip during power down of the portion of the integrated circuit chip; and on power up, restoring the configuration information of each debug unit to that debug unit prior resuming operation of that debug unit and the peripheral circuit connected to that debug unit.

Abstract: Roughly described, an integrated circuit chip comprises a plurality of peripheral circuits, each peripheral circuit connected to a respective debug unit, the respective debug unit configured to generate debug information of that peripheral circuit; and a plurality of separate stores for receiving debug information, storing debug information, and outputting debug information; wherein in response to a single trigger signal, the debug units are configured to stream their generated debug information to the plurality of separate stores; and wherein each of the plurality of separate stores is configured to receive debug information at a higher stream rate than it outputs debug information.

Abstract: A method of functionality testing system circuitry on an integrated circuit chip, the system circuitry comprising a plurality of sub-circuits and the integrated circuit chip further comprising debugging circuitry, the debugging circuitry comprising variability circuitry. The method comprises: at the system circuitry, performing a function by the sub-circuits performing concurrent actions; at the variability circuitry, altering relative timing of the concurrent actions so as to increase the likelihood of one or more errors in the system circuitry's performance of the function; and at the debugging circuitry, recording one or more errors in the system circuitry's performance of the function.

Abstract: Roughly described, a method of powering down a portion of an integrated circuit chip, the portion of the integrated circuit chip comprising a plurality of peripheral circuits, each peripheral circuit being connected to a respective debug unit, the method comprising: prior to power down, extracting from each debug unit configuration information of that debug unit; storing the configuration information of the debug units in a memory on the integrated circuit chip during power down of the portion of the integrated circuit chip; and on power up, restoring the configuration information of each debug unit to that debug unit prior resuming operation of that debug unit and the peripheral circuit connected to that debug unit.

Abstract: An integrated circuit chip device comprising: system circuitry; debugging circuitry configured to debug the system circuitry, the debugging circuitry being segmented into zones; wherein the debugging circuitry comprises an interconnect fabric configured to route debug messages through a zone from a zone entry node of the interconnect fabric to a zone exit node of the interconnect fabric; and wherein the debugging circuitry is configured to, on receiving a debug message at a zone entry node that is shorter than a specified length, modify the debug message to form a modified debug message by increasing the length of the debug message to the specified length.

Abstract: A method of validating functional testing of system circuitry on an integrated circuit chip, the system circuitry configured to perform a plurality of functions, the integrated circuit chip further comprising debugging circuitry under the control of a debug controller, the debugging circuitry comprising at least one debug unit. The method comprises: at the system circuitry, performing one of the plurality of functions; applying a debug configuration to the at least one debug unit; and at the at least one debug unit, monitoring for a characteristic in the system circuitry's performance of the one of the plurality of functions according to that debug configuration, and reporting to the debug controller.

Abstract: A method of validating functional testing of system circuitry on an integrated circuit chip, the system circuitry configured to perform a plurality of functions, the integrated circuit chip further comprising debugging circuitry under the control of a debug controller, the debugging circuitry comprising at least one debug unit. The method comprises: at the system circuitry, performing one of the plurality of functions; applying a debug configuration to the at least one debug unit; and at the at least one debug unit, monitoring for a characteristic in the system circuitry's performance of the one of the plurality of functions according to that debug configuration, and reporting to the debug controller.

Abstract: A method of functionality testing system circuitry on an integrated circuit chip, the system circuitry comprising a plurality of sub-circuits and the integrated circuit chip further comprising debugging circuitry, the debugging circuitry comprising variability circuitry. The method comprises: at the system circuitry, performing a function by the sub-circuits performing concurrent actions; at the variability circuitry, altering relative timing of the concurrent actions so as to increase the likelihood of one or more errors in the system circuitry's performance of the function; and at the debugging circuitry, recording one or more errors in the system circuitry's performance of the function.

Abstract: Roughly described, an integrated circuit chip comprises a plurality of peripheral circuits, each peripheral circuit connected to a respective debug unit; a shared hub; and between each respective debug unit and the shared hub, a single physical interface configured to transport both configuration data and event data, wherein the interface is configured such that if an event occurs while the interface is transporting configuration data, the interface interrupts the transport of the configuration data in order to transport the event data.

Abstract: Roughly described, a method of controlling transportation of debug data on an integrated circuit chip. The chip has a shared hub and a number of peripheral circuits. Each peripheral circuit is connected to a respective debug unit, and between each debug unit and the shared hub there is an interface configured to transport data messages over each of a number of prioritized flows. In the method, still roughly described, control data for controlling the state of a debug unit is transported on a priority flow having a first priority, and debug data output by a debug unit as a result of debugging the peripheral circuit connected to that debug unit is transported on a flow having a second priority, the first priority being higher than the second priority.

Abstract: Roughly described, a method of sending a message from a source unit to a destination unit both forming part of a hierarchical debug architecture on a chip, the units in the hierarchy using a protocol in which each unit has an internal address which is the same base address, and in which each unit addresses other units using addresses derivable relative to that unit's internal address given positions of other units in the hierarchy, comprising: the source unit in a first level of the hierarchy sending a message comprising a destination address of the destination unit, the destination address being relative to the source unit's internal address, and an intermediate unit in a second level of the hierarchy: adding an offset to the destination address to form a rebased destination address, being relative to the intermediate unit's internal address, and routing the rebased message onto the destination unit.

Abstract: A data processing apparatus having processing circuitry and debug circuitry is debugged by operating the processing circuitry to generate data. The debug circuitry is employed to generate trace elements indicative of the operation of the processing circuitry. Trace elements are caused to be output from the data processing apparatus over a communication bus capable of connecting a plurality of devices. The communication bus is controlled by a protocol for data interchange requiring data interchange from any device on the communication bus to be controlled by a single processing system. The passing of the trace elements onto the communication bus is controlled using an interface unit of the debug circuitry. The interface unit comprises a controller arranged to allow each of the interface unit and processing circuitry to be separate processing systems which can each independently control data interchange from the data processing apparatus.