Abstract: A system comprising a host, a target and connection means therebetween. The host has means for providing a clock signal, first output means for outputting said clock signal to said target via said connection means and second output means for outputting data to said target via said connection means, said data being clocked out by said clock signal, said target having first input means for receiving said clock signal from said host, second input means for receiving said data from said host and first output means for outputting data to said host via said connection means. The host further comprises input means for receiving said data from said target, and oversampling means for oversampling the received data from the target and controlling the clocking in of said data received from said target in dependence on said oversampling.

Abstract: A comparator circuit with comparing means for comparing first and second voltages, has current source circuitry for providing current to said comparing means, said current source circuitry having an input for receiving a clock signal having first and second states, whereby the comparing means starts to compare the first and second voltages when the clock signal makes a transition from the first state to the second state; and means for determining when said comparing means has completed a comparison of said first and second voltages and for switching off said current source circuitry and hence said comparing means when said comparison has been completed.

Abstract: An interrupt management system includes a first down-counter which decrements in value in response to a clock signal to zero. When the value of the down-counter is equal to zero the down-counter is reset to a predetermined value X and an interrupt request signal is produced. The interrupt management system also includes a second down-counter which decrements in value from a predetermined value Y, where Y>X, in response to the clock signal. The interrupt request signal is received by a processor which services the interrupt and generates an interrupt serviced signal. The interrupt serviced signal is received by a controller which also receive the value of the second down-counter. Using the received value from the second down-counter, the controller can determine if an interrupt request has been missed and also determine the latency period for servicing an interrupt request.

Abstract: A semiconductor integrated circuit, including a test scan arrangement has a plurality of scan chains arranged in pairs. These scan chains have input terminals for receiving test patterns, and outputs provided to compression logic such as a distributed XOR tree multiple input shift register to provide an output which is a compressed signal derived from the output test patterns. In an alternative configuration, the first scan chain of each pair is connected to the second scan chain of each pair, and the input terminal of the second scan chain becomes the output terminal. Thereby creating a longer scan chain of the first and second scan chains together with one input terminal and one output terminal. The two loads allow for efficient scanning in the first mode, or debugging to determine the position of a fault in the second mode.

Abstract: An method of arranging address decoders in an improved manner in an integrated circuit memory is discussed. In the integrated circuit memory the address lines extending from the address circuitry of the integrated circuit memory are connected to address decoders, each word line of the memory being connected to an address decoder. The address decoders are connected to the address lines in a certain combination such that only one of the address lines is connected to adjacent address decoders. When connected in this manner the average propagation delay of each address line is substantially uniform. By reducing the maximum propagation delay in comparison with previously known arrangements of address decoders the speed at which the memory can be operated is increased.

Abstract: A system and method for communicating with an integrated circuit is provided that allows an integrated circuit to communicate debugging information and system bus transaction information with an external system. The system may include an interface protocol that provides flow control between the integrated circuit and the external system. The system may include a high-speed link and/or a JTAG link for communicating information. A link may be automatically selected by a debug circuit, or selected by an on-chip device or external system. The high-speed link enables real-time collection of trace information. Links may be memory-mapped, such that on-chip devices and other devices attached to the system bus may access the external system. The high-speed link may also operate at a rate which is integrally coupled with a rate of the processor or system bus. Further, the high-speed link may be adapted to change speeds in response to a change in operating speed of the system bus or processor.

Abstract: An integrated circuit including serial data input and output pins, on-chip functional circuitry and test logic, a test access port controller, and a data adaptor. The test access port controller is connected to effect communication of serial data across tile chip boundary via the input and output pins and is connectable to the test logic to effect communication of serial test data off-chip. The data adaptor is connectable to the input and output pins via the test access port controller. The data adaptor includes an interface for communicating data in the form of serial bits with the test access port controller under control of a first clock signal, and an interface for communicating data in the form of successive sets of parallel data and control signals with the on-chip functional circuitry under control of a second clock signal that is generated independently of the first clock signal.

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: A sense amplifier circuit has two inputs for connection to complementary bit lines and an output terminal. The circuit comprises control circuitry responsive to control input for selectively tristating the output terminal.

Abstract: A switching circuit is discussed that has an improved switching time in comparison with switching circuits of a known type. The circuit comprises three switches connected in series, the first switch being connected to an upper power supply and the third switch being connected to a lower power supply. The output of the circuit is connected to a circuit node located at the connection between the second and third switch. The input to the switching circuit is also connected to the third switch and additionally connected to a control circuit which provides a further output to control the first switch. The second switch is responsive to the voltage at the circuit node such that the second switch only conducts when the voltage at the output node falls below the upper supply voltage.

Abstract: A method of designing an addition circuit, and an addition circuit designed according to the method are described. The design technique is optimised to facilitate design of an addition circuit of minimum depth. The design technique takes into account the number of logical stages of the addition circuit and the manner in which those stages are connected by spanning paths to create fan-out nodes. The number of fan-out nodes per level can be optimized. For bit lengths n, the number (m+2) of logical stages is n=2m+1 and for bit lengths n not of a binary order, the number (m+2) of logical stages is nb0=2m+1, where nb0 is the next largest binary order after n.

Abstract: A mute switch including a field effect transistor receiving a mute control signal at its gate for selectively supplying an audio signal from an input node to an output node. A bipolar transistor is connected between the input node and the FET for reducing the voltage level of the audio signal prior to its application to the input node, and a further bipolar transistor is connected between the FET and the output node for raising the voltage level of the audio signal prior to its application to the output node. This serves to maintain the DC bias level of the audio output signal independently of the status of the mute control signal.

Abstract: A circuit for generating an output voltage proportional to temperature with a required gradient, the circuit including a first stage arranged to generate a first voltage which is proportional to temperature with a predetermined gradient but has a positive value when the temperature falls below zero and a second stage connected to the first stage and including a differential amplifier having a first input connected to receive the first voltage and a second input connected to receive a feedback voltage which is derived from an output signal of the differential amplifier via an offset circuit which introduces an offset voltage such that the output signal of the differential amplifier provides at an output node the output voltage which has a negative variation with negative temperatures.

Abstract: A circuit for providing a control signal for a load includes a first switch having a first and a second state, a second switch having a first and a second state coupled to said first switch, a load connected to said first and second switches, protection circuitry for protecting said load from excessive voltage and circuitry for switching said first switch. The circuit is arranged so that when the first switch is in the first state current flows from the load to the first switch and the switching circuitry is arranged to switch the first switch to the second state when the voltage across the load reaches a predetermined value.

Abstract: A circuit for generating an output voltage which is proportional to temperature with a required gradient is disclosed. The circuit relies on the principle that the difference in the base emitter voltage of two bipolar transistors with differing areas, if appropriately connected, can result in a current which has a positive temperature coefficient, that is a current which varies linearly with temperature such that as the temperature increases the current increases. It is important to maintain a stable internal line voltage in the face of significant variations in a supply voltage to the circuit. This is achieved herein by providing control elements appropriately connected to a differential amplifier. The stable internal supply voltage can be used to power a subsequent stage of the circuit for fine control of the gradient of the voltage proportional to temperature.

Abstract: A graphic processor having an index processing unit for pre-processing a list of vertices making up a three-dimensional image. The method of pre-processing comprising the following steps. First, decomposing the three-dimensional image into a plurality of primitive elements each defined by a set of vertices, each vertex comprising vertex information stored in a vertex storage area and addressable by a vertex index. Then receiving said vertex indices and creating a set of unique indices identifying a batch of vertices and loading only the vertices corresponding to said unique indices into the vertex storage area. Finally creating transformed primitive elements from transformed vertex information addressed in the vertex storage area using the unique indices.

Abstract: A current source using a bandgap voltage circuit includes a current gain circuit between the output of the bandgap circuit and the current output transistor. On-off control is provided by a switchable bias circuit providing an ON potential to start the bandgap and a clamping circuit opening the feedback loop.

Abstract: A differential amplifier circuit comprises: an amplifying section including first and second current branches and an output stage which comprises a current sinking element and a control element. The circuit also includes a current limiting section which comprises a current detecting element connected to detect the current through the current sinking element and arranged to drive the current limiting element when the detected current exceeds a predetermined threshold to inject current at the collector of the transistor in the first current branch.

Abstract: A clock source selector for selecting either a first clock signal A or a second clock signal B in accordance with a switch request signal includes three retiming circuits each consisting of two clocked flip-flops. The switch request signal is first retimed relative to clock A to give a signal P, is then retimed relative to clock B to give a signal Q, and finally is retimed relative to clock A to give a signal R. Selector circuitry operates such that when signal Q is asserted, the second clock signal B is output, when neither signal P nor signal R, as combined by a NOR gate, are asserted, the first clock signal A is output, and at other times a zero level is output. The clock source selector can be used in an integrated circuit to form a glitch-free multiplexer.

Abstract: A digital phase comparator circuit that determines and adjusts the relative phase of two digital clock signals derived from the same digital clock. The circuit having two inputs, one connected to receive each of the clock signals to be compared and including a latch circuit to receive one clock signal at the clock input, and the other clock signal at a data input. The latch circuit is arranged so that the output is equal to the signal at the data input when measured at the clock edge. The output is therefore a logic “1” when the second clock leads the first clock, and a logic “0” when the second clock lags the first clock.