Abstract: A priority encoder for generating a priority-encoded address which identifies the highest priority request line. According to one priority scheme, the active request line having the lowest address has the highest priority. The priority encoder is capable of generating the priority-encoded address by determining information corresponding to the most significant bits of the priority-encoded address and using this information in the computation of less significant bits of the priority-encoded address. Using purely combinatorial logic, including switch elements, the priority encoder is capable of computing lower order bits using feedback signals resulting from the computation of higher order bits, allowing successive computation of priority-encoded address bits, without necessitating the use of clocks or delay elements.

Abstract: A mixed signal phase locked loop is optimized for fast settling and low noise sensitivity. To this end, this device has a digital wide range delay line and a low gain per stage adjust. When first activated, the loop calibrates the digital delay line to its nominal delay characteristic. This delay line, together with the linear low gain per stage adjust, constitutes the internal oscillator of the phase locked loop. After achieving nominal delay, the oscillator uses the low gain per stage adjust to lock to a desired reference or a submultiple thereof. According to the preferred embodiment, the loop locks its internal 125 MHz oscillator to a 25 MHz reference. After achieving lock, the loop performs synchronous data recovery by locking to an incoming data stream, instead of the internal reference, and performing bit framing. In case of losing lock, the phase locked loop of the present invention is capable of recalibrating itself and regaining lock in under 3 microseconds.

Abstract: A circuit and a method for detecting the presence of multiple active match lines in a content addressable memory is disclosed. The circuit includes at least one bus group for expressing a unary-encoded address portion of an active match line and, for each match line, an encoding circuit capable of activating a single member of each bus group according to the address of that match line when that match line is active. The multiple match detection circuit advantageously uses the property that each match line has a unique address, and therefore if there is more than one active match line, at least one bus group will have at least two active members. The multiple match detection circuit further comprises, for each bus group, an bus group detection-OR circuit for computing the logical bus group detection-OR of the members of that bus group.

Abstract: An overvoltage tolerant CMOS tristate output buffer capable of withstanding tristate overvoltages without reverse currents or latch-up, the output buffer having a stabilized protection circuit for driving the N-well and gate of the P-channel driver transistor to the output pad voltage when the output pad voltage becomes excessive. The stabilized protection circuit includes a hysteresis circuit for controlling switch transistors which bias the N-well. The presence of the hysteresis circuit causes the protection circuit to have an input hysteresis characteristic, thus preventing excessive switching of the N-well biasing transistors when the output pad voltage varies near the output buffer power supply voltage during tristate.

Abstract: A mixed-mode, overvoltage tolerant input buffer for interfacing to a tristate bus line is disclosed, the input buffer having a bus hold feature for maintaining the state of the input buffer output and bus line when the bus line enters into the tristate mode, the input buffer being capable of suppressing leakage currents from the bus input through the bus hold circuit to the input buffer power supply during overvoltage conditions. The bus hold circuit has a feedback inverter coupled between the output and the bus input for providing a stabilizing feedback signal to the bus input, the inverter being powered by a source voltage which is selectively coupled to the input buffer power supply, the source voltage being isolated from the input buffer power supply during overvoltage conditions.

Abstract: A semiconductor memory device is disclosed which is partitionable into random access memory (RAM) and content addressable memory (CAM) subfields, and with which incremental comparisons may be efficiently conducted. The apparatus generally includes a memory array of N data storage locations of M bits each which may be divided into predefined segments, a means for comparing a search word with all data words stored in the array, a means for generating a match signal when the bits of the search word match the bits of the data words, and a configuration register and a plurality of transfer gates for selecting which of the predefined array segments are to function solely as random access memory. The apparatus may additionally include a plurality of storage means, each corresponding to a segment of the memory array, for storing the match signals generated from that corresponding segment during a comparison.

Abstract: A fast transmission, integrated circuit switching device responsive to at least one external on/off control signal, and including a first input/output node, and a second input/output node, the switching device operative to pass or block the bidirectional transmission of external data signals between the first node and the second node, the switching device comprising a bidirectional field-effect transistor; a first scan cell; and a second scan cell; whereby input and output data signals of the switching device may be sensed and stored.

Abstract: The input/output circuit cells of a master-slice gate array device have the same diffusion and gate regions as the basic transistors so that the input/output of the device may be defined at the metallization stage rather than at the time the diffusion regions are formed. Thus a single size master-slice circuit device need to be kept in inventory. The array size is selected in accordance with the customer's specification and the inputs/outputs are defined accordingly using CAD. Thereafter, the die may be scribed into smaller. The transistors for sea-of-gate structures containing a pair of long channel transistors whose drain, gate and source regions lie on a single grid or track of the CAD design tool. By using a long channel transistor in the feedback loop of a memory cell, gating transistors may be eliminated to reduce transistors required for latches.

Abstract: A read signal and write signal for a FIFO each has a flag generating edge and a preceding edge. The read or write counter in an empty of full flag generator responds to the preceding edge of the read or write signal so that the empty or full comparator of the generator may generate an updated empty or full flag value before the onset of the flag generating edge. The empty or full flag generator also includes a gate and a pulse generating circuit. The pulse generating circuit responds to the flag generating edge by generating an enabling signal enabling the gate to pass the comparator output to a latch. When the empty or full comparator indicates that a FIFO is empty or full, the comparator output passed by the gate will force the output high, thereby asserting an empty flag or a full flag. The empty flag generator also includes a second pulse generating circuit which updates the empty flag signal to indicate a non-empty FIFO in response to each write signal.

Abstract: A fast switching device for passing or blocking signals between two input/output ports includes a transistor having a first and a second terminal and a control terminal. The first and second terminals are connected between the two ports. The transistor passes signals between the ports when the transistor is turned on and blocks the passage of signals between the ports when the transistor is turned off. The resistance between the first and second terminals is less than about 10 ohms when the transistor is turned on. The device further includes a driver for controlling the control terminal of the transistor for turning it on or off. Preferably the capacitance between the first or second terminal and a reference potential is less than about 50 pF.

Abstract: A metal silicide layer in or on a body of silicon wafer is used for interconnecting two or more CMOS circuit devices. In addition to a polysilicon layer and a metal layer, the metal silicide layer provides an additional layer of local interconnect which can be performed at high density to reduce the size of the die while including the same number of circuit devices. An amorphous silicon layer doped at selected regions may be used as an additional interconnect.

Abstract: To reduce the access time of a FIFO, a storage device is provided for storing pre-loaded data to be read from the memory array of the FIFO. Thus during each read operation, the pre-loaded data in the storage device is read and the next unit of data to be read during the next read operation is pre-loaded from the array into the storage device. A second storage device is provided for storing the first unit of data written into the array after the array is empty. Thus during the first read operation after the array is rendered non-empty by one or more consecutive write operations, the first unit of data stored in the second storage device is read during the first read operation. This avoids reading garbage from the first storage device which is pre-loaded during the last read operation before the FIFO is empty.

Abstract: A metal silicide layer in or on a body of silicon wafer is used for interconnecting two or more CMOS circuit devices. In addition to a polysilicon layer and a metal layer, the metal silicide layer provides an additional layer of local interconnect which can be performed at high density to reduce the size of the die while including the same number of circuit devices. An amorphous silicon layer doped at selected regions may be used as an additional interconnect.