Abstract: Apparatus for testing an integrated circuit, the integrated circuit comprising a plurality of semiconductor memory cells connected by a common word-line, each memory cell comprising: respective first and second transistors in cross-coupled arrangement to form a bistable latch, the drain of the first transistor representing a respective first node for storing a high or low potential state and being connected to a respective first semiconductor arrangement for replacing charge leaked from the first node and being connected to a respective first switching device, activatable by the common word-line, for coupling the respective first node to a respective first bit-line, the drain of the second transistor representing a respective second node for storing a high or low potential state and being connected to a respective second semiconductor arrangement for replacing charge leaked from the respective second node and being connected to a respective second switching device, activatable by the common word line, for cou

Abstract: An integrated cache memory circuit is provided comprising a tag RAM, a comparator and a data RAM. Each of the tag RAM and the date RAM have an array of memory cells and plural sense amplifiers. Each memory cell of the RAMs is connected via a respective bit line to one of the plural sense amplifiers. The sense amplifiers of the tag RAM have respective outputs coupled to a first input of the comparator. The comparator having a second input for address information and an output for selectively enabling data output from sense amplifiers of the data RAM. The memory cells of the tag RAM are arranged to have a higher current drive than the memory cells of the data RAM.

Abstract: To establish whether a precharged node remains isolated or alternatively is subject to discharge, the conventional circuit allows uncertainty. For a period after evaluation starts, the conventional circuit will give a tentative result that may subsequently turn out to be wrong. During evaluation power is dissipated. A differential offset dynamic comparator and timing circuit are used to evaluate whether the node is being discharged. Because the comparator has an offset, much smaller deviations from the precharge potential can be sensed: because it is dynamic, it does not consume steady state current. The timing circuit permits precise knowledge of when to look at the output: before the timing period has elapsed, the result is known to be invalid.

Abstract: The present invention relates to a memory having sense amplifiers and data latches, the data latches being used in a test mode to form a signature register. In a normal operation mode, the data latches are form write data latches.

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: Apparatus for testing an integrated circuit, the integrated circuit comprising a plurality of semiconductor memory cells connected by a common word-line, each memory cell comprising: respective first and second transistors in cross-coupled arrangement to form a bistable latch, the drain of the first transistor representing a respective first node for storing a high or low potential state and being connected to a respective first semiconductor arrangement for replacing charge leaked from the first node and being connected to a respective first switching means, activatable by the common word-line, for coupling the respective first node to a respective first bit-line, the drain of the second transistor representing a respective second node for storing a high or low potential state and being connected to a respective second semiconductor arrangement for replacing charge leaked from the respective second node and being connected to a respective second switching means, activatable by the common word line, for coupl

Abstract: A cache memory and method for operating a cache memory are provided which comprise a tag RAM, tag RAM sense amplifier circuitry, data RAM sense amplifier circuitry and decision circuitry. Timing difficulties exist in determining whether or not a hit has occurred and in outputting the data from the data RAM upon occurrence of a hit. Upon addressing a tag entry and the corresponding data entry, the tag information is output from the tag RAM and is compared with input address information. A decision is reached as to whether or not identify exists. Only when the result of that decision has been validly determined can data be output.

Abstract: A level shifter uses a current mirror as a current switch connected to the drains of two oppositely-driven FETs. A switch selectively connects the current mirror to its power supply so that no quiescent DC current flows.

Abstract: An integrated current reference comprises two current mirrors, the gate source voltage of one of the current mirrors being offset by a voltage reference element, which in an embodiment consists of an on MOSFET.

Abstract: Test circuitry for testing an integrated circuit, the integrated circuit being configurable to accept input data from stimulus scan cells and to provide output data to response scan cells, the test circuitry including stimulus circuitry for providing test data to the integrated circuit; input selection means operable to control which of the test data and the input data are received at the integrated circuit; capture circuitry for capturing output data from the integrated circuit and generating response data; output selection means operable to select which of the output data and the response data are received by the response scan cells.

Abstract: To establish whether a precharged node remains isolated or alternatively is subject to discharge, the conventional circuit allows uncertainty. For a period after evaluation starts, the conventional circuit will give a tentative result that may subsequently turn out to be wrong. During evaluation power is dissipated. A differential offset dynamic comparator and timing circuit are used to evaluate whether the node is being discharged. Because the comparator has an offset, much smaller deviations from the precharge potential can be sensed: because it is dynamic, it does not consume steady state current. The timing circuit permits precise knowledge of when to look at the output: before the timing period has elapsed, the result is known to be invalid.

Abstract: A circuit compares a first voltage and a second voltage using a comparator. The comparator has a current divider for dividing a bias current in accordance with the values of the first and second voltages, and for providing two currents. The comparator also has a current differentiation circuit for receiving the two currents and providing an output signal dependent upon the difference between the currents. At least one of the current divider and current differentiation circuits are arranged to weight one of the two currents with respect to the other current so that the output signal is only provided when the difference between the first and second voltages exceeds an offset value. A bias generator is provided which includes a second comparator having similar components in the same configuration as the comparator.

Abstract: A complementary logic circuit is provided which provides improved switching times over known complementary logic circuits. The circuit includes a further n-type transistor connected in series between a p-type and an n-type transistor. This additional n-type transistor has its gate permanently connected to an upper supply voltage, Vdd. When switching occurs the n-type transistor is effectively open circuit. This allows the first n-type transistor to switch on by a substantial amount quite quickly without ‘fighting’ the presently conducting p-type transistor. When the first n-type transistor has been turned substantially on second transistor becomes conductive. Then the p-type transistor is substantially turned off and no longer opposes the turning on of the first n-type transistor.

Abstract: A ratio logic gate has a current mirror controlled by the pull-down transistors and supplying a half size pull-down transistor. When one or more of the input pull-down transistors is on, the mirror current overcomes the output pull-down transistor to provide a high potential output. Process tolerances between p and n type devices is thus avoided.

Abstract: A flip-flop circuit comprises a pair of cross-coupled inverters, each of which has a respective FET connected in series between it and the reference terminal, each inverter driving a transistor of an output inverter.

Abstract: A wordline driver has enable circuitry optimized for positive-going input transitions and disable circuitry optimized for transitions in a disable input which would cause the output to become disabled. The optimization is achieved by suitably dimensioning the transistors in the respective enable and disable circuits for suitable current-carrying ability.

Abstract: A miss detector for a content addressable memory has plural input lines connected across points with the memory output lines. The detector input lines are disposed in pairs of true and false lines, and gating circuitry gates together the true and false pairs to provide a miss error message.

Abstract: An output circuit which can minimize the delay in combining two clocks comprises a multiplexer with a flip flop connected to one input and a clocked latch connected to the other. The clocked latch is transparent during one clocking state so that changes to its input appear directly at its output.

Abstract: An integrated current reference circuit uses two current mirror circuits, in which one of the transistors of one of the current mirrors has a back gate connection to the power rail, the drain-source path being connected to the power rail via a voltage offset element.