Stmicroelectronics (research & Development) Limited

Stmicroelectronics Gmbh

Tariq Kurd

Mark Owen Homewood

Paul Elliott

A semiconductor integrated circuit includes a hardware mechanism arranged to ensure that associations between instructions and data are enforced so that a processor cannot fetch data from an instruction that is not authorized to do so. A Memory Protection Unit stores entries comprising instructions and associated data memory ranges. A hardware arrangement impairs the operation of the circuit if the processor attempts to make a data fetch from an instruction that is outside the range associated with data in a Memory Protection Unit. Such functioning may be by issuing a chip reset. The Memory Protection Unit may be implemented in a Memory Management Unit having an extension so as to store a validity flag. The validity flag may only be set by a secure process such as the CPU well entrusted code or by a separate trusted hardware source.

Integrated circuit with restricted data access

A cache memory comprises a first set of storage locations for holding syllables and addressable by a first group of addresses; a second set of storage locations for holding syllables and addressable by a second group of addresses; addressing circuitry operable to provide in each addressing cycle a pair of addresses comprising one from the first group and one from the second group, thereby accessing a plurality of syllables from each set of storage locations; and selection circuitry operable to select from said plurality of syllables to output to a processor lane based on whether a required syllable is addressable by an address in the first or second group.

Cache memory

Combining circuitry for combining a plurality of multi-bit partial product terms in a multiplier circuit includes a plurality of compression columns, each column receiving a plurality of partial product term bits. At least one compression column includes: a first circuit arranged to receive a first set of the plurality of partial product term bits for the at least one compression column, the first circuit further arranged to combine the first set of term bits to produce a first combined term bit set; and a second circuit arranged to receive a second set of the plurality of term bits for the at least one compression column and all of the first combined term bit set.

Multiplication circuitry

An arithmetic unit comprising: an encoding circuit arranged to receive first and second operands each having a bit length of m bits and to generate therefrom a number n of partial products of bit length of 2m bits or less; an addition circuit having 2m columns each having n inputs, wherein bits of said partial products are applied to said inputs for combining said partial products into a result leaving certain of said inputs unused; and a rounding bit generator connected to supply a rounding bit to at least one of said unused inputs in one of said in columns at a bit position to cause said result to be rounded.

Performing rounding in an arithmetic operation

A combining circuit and method combines a plurality of terms in a multiplier circuit. The combining circuit includes a first circuit, arranged to receive a first set of the plurality of terms and to combine the first set of terms to produce a first combined term set. The combining circuit also includes a second circuit, arranged to receive a second set of the plurality of terms and to combine the second set of terms to produce a second combined term set. The combining circuit further includes a third circuit, arranged to receive the first and second combined term sets and to combine the first and second combined term sets to produce a third combined term set. The combining circuit outputs the first combined term set as a first combination result and the third combined term set as a second combination result.

Combining circuitry

An arithmetic unit for selectively implementing one of a multiply and multiply-accumulate instruction, including a multiplier, addition circuitry, a result register, and accumulator circuitry. The multiplier arranged to receive first and second operands and operable to generate multiplication terms. The addition circuitry for receiving multiplication terms from the multiplier and operable to combine them to generate a multiplication result. The result register for receiving the multiplication result from the adder. The accumulator circuitry connected to receive a value stored in the result register and an accumulate control signal which determines whether the arithmetic unit implements a multiply or a multiply-accumulate instruction.

Multiply-accumulate unit and method of operation

The invention provides circuitry for carrying out a square root operation. The circuitry utilizes iteration circuitry for carrying out a plurality of iterations. The iteration circuitry includes a circuit for calculating a root multiple, the root multiple being a multiple of a current quotient value. The root multiple is used by the iteration circuitry to modify a current remainder.

Circuitry for carrying out a square root operation

Circuitry is provided for performing a non-arithmetic operation in relation to at least one number. The circuitry includes a first part for carrying out the non-arithmetic operation in relation to the at least one number, the first part providing a result. A second part is arranged to identify at least one characteristic of the at least one number and to provide an output and correction circuitry for providing, if necessary, a correct result in dependence on the output of the second part, wherein said first and second parts are arranged to operate in parallel.

Circuitry and method for performing non-arithmetic operations

Circuitry for carrying out an arithmetic operation requiring a plurality of iterations, such as division or square root operations, utilizes N sets of iteration circuitry arranged one after the other so that at least one of the sets of iteration circuitry receives an output from a preceding one of the sets of iteration circuitry. Each of the sets of iteration circuitry includes at least one adder part, wherein a full adder is provided by at least one part in one of the sets of iteration circuitry and a second part in a succeeding one of the sets of iteration circuitry.

Circuitry for carrying out division and/or square root operations requiring a plurality of iterations

The invention provides circuitry for carrying out a square root operation and a division operation. The circuitry utilizes common iteration circuitry for carrying out a plurality of iterations and means for identifying if an square root operation or a division operation is to be performed. The iteration circuitry is controlled in accordance with whether a square root or division operation is to be performed.

Circuitry for carrying out square root and division operations

The invention provides circuitry for carrying out at least one of a square root operation and a division operation. The circuitry utilizes a carry slave adder and a carry propagate adder part. The carry save adder and the carry propagate adder part are arranged in parallel.

Growing community of inventors

Bristol, United Kingdom

Tariq Kurd