Digital Equipment Corporation

Steven W Butler

Hamid Partovi

William Ralph Wheeler

Kaizad R Mistry

David Benjamin Krakauer

Rajesh Khanna

Michael A Case

Michael Leary

Laun Q Tran

Luan Tran

An ESD protection device is provided which includes a self referencing modulation circuit for controlling its operation. The modulation circuit includes a diode stack coupled to a resistor and further coupled to an inverter powered by the signal pad voltage in one embodiment, or an odd plurality of series connected inverters powered by the signal pad voltage in an alternate embodiment. The inverter chain is coupled to the ESD clamp. The modulation circuit requires no reference supply voltage to operate. The ESD protection circuit shunts currents associated with ESD events away from ICs as well as clamping I/O pad voltages to acceptable levels during an ESD event.

Self-referencing modulation circuit for CMOS integrated circuit

A self-timed logic device which produces internal control and timing signals in response to an external signal is described. The circuit includes means responsive to a pulse signal for providing control and timing signals and means responsive to a change in state of a signal fed to said device for providing said pulse signal. The means for providing said pulse further includes means for selectively changing timing characteristics of said device in response to external tuning signals fed to the device. In a preferred embodiment the logic device is a static random access memory.

Static random access memory having tunable-self-timed control logic

A semiconductor memory device according to the invention includes a main memory comprising a number of memory sub-arrays, each coupled to an address and a data bus, for providing or receiving data to an intermediate interface unit. The intermediate interface unit provides data to and receives data from an output bus. Also included in the semiconductor memory device is redundancy circuit including a redundant memory coupled to the output bus for storing a subset of data from one of the sub-arrays in the event that the sub-array is defective. The redundancy circuit additionally includes address fuses for storing the sub-array addresses of the subset of data to be stored in the redundant storage, and compare circuitry coupled to the address bus for comparing the address bus to the stored array addresses to determine if there is a match. In the event of a match, the compare circuitry provides an index to the redundant storage unit and enables it to provide data to or receive data from the output bus, while precluding the intermediate interface from providing data from the main memory array to the output bus.

Method and apparatus using mapped redundancy to perform multiple large

A voltage level conversion buffer circuit including a first and a second transistor each having a gate, a drain, and a source. The drain of the first transistor and the gate of the second transistor are connected together to provide an input to the buffer circuit, and the gate of the first transistor and the drain of the second transistor are connected to a supply voltage. The sources of the first and second transistors are connected together to provide an output for the buffer circuit.

Voltage level converting buffer circuit

A tag comparator and bank selector for a set-associative cache in a computer system operates in a minimum time so that a cache hit or miss signal is generated early in a memory cycle. The data memory of the cache has two (or more) banks, with a tag store for each bank, and the two banks are accessed separately and in parallel using the index (low order address bits) while the tag translation is in progress. Two bit-by-bit tag compares are performed, one for each tag store, producing two multibit match indications, one bit for each tag bit in each tag store. These two match indications are applied to two separate dynamic NOR gates, and the two outputs applied to a logic circuit to detect a hit and generate a bank-select output. There are four possible outcomes from the compare operation: both banks miss, left bank hits, right bank hits, and both banks hit. The later condition indicates a possible ambiguity, and neither data item should be used, so a miss is signalled. The comparator is in large part self-timed using a flow-through design, as distinguished from being enabled on clock edges. Delay elements in the bank select logic allow the banks to be timed against each other, and current limiters are employed to equalize the timing of miss signals, regardless of the number of match lines switching high (which is data dependent). An address producing 19-of-20 match bits will result in a NOR gate output of about the same timing as an address producing no match bits, even though the former will turn on only one transistor to discharge the precharged output node of the NOR gate, whereas the later will turn on twenty paths for discharge. Although a two-way set associative cache is shown herein as an example embodiment, one of the features of the invention is that higher levels of associativity, e.g., four-way and eight-way, are equally well accommodated.

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Marlboro, MA, United States of America

Steven W Butler