Apparatus and method for performing linear interpolation

A method for performing linear interpolation within an apparatus, comprising:

• providing a multiplier array to implement a multiply accumulate operation in order to multiply together a multiplier value and a multiplicand value, and add an accumulate value;
• arranging the multiplier array to comprise a plurality of rows, each row comprising multiplexer circuitry and adder circuitry, with the multiplexer circuitry being arranged to select, in dependence on a control input, one of a first multiplexer input value and a second multiplexer input value to provide as a first adder input value to the adder circuitry, in each row other than an initial row the adder circuitry further being arranged to receive as a second adder input value at least a portion of a result value produced by the adder circuitry in a preceding row of the multiplier array;
• changing the mode of operation of the apparatus between a multiplication mode where the multiplier array implements the multiply accumulate operation and a linear interpolation mode where the multiplier array is used to implement a linear interpolation operation between a lower limit input value and an upper limit input value based on a weighting value;
• when in the multiplication mode, arranging each row of the multiplier array such that the control input for the multiplexer circuitry of that row is provided by an associated bit of the multiplicand value selected for that row, the first multiplexer input value is set to 0, and the second multiplexer input value is set to the multiplier value;
• and
• when in the linear interpolation mode, arranging each row of the multiplier array such that the control input for the multiplexer circuitry of that row is provided by an associated bit of the weighting value selected for that row, one of the first multiplexer input value and the second multiplexer input value is set to the lower limit input value, and other of the first multiplexer input value and the second multiplexer input value is set to the upper limit input value.

An apparatus comprising:

• multiplier array means for implementing a multiply accumulate operation in order to multiply together a multiplier value and a multiplicand value, and add an accumulate value;
• the multiplier array means comprising a plurality of rows, each row comprising multiplexer means and adder means, with the multiplexer means for selecting, in dependence on a control input, one of a first multiplexer input value and a second multiplexer input value to provide as a first adder input value to the adder means, in each row other than an initial row the adder means further being arranged to receive as a second adder input value at least a portion of a result value produced by the adder means in a preceding row of the multiplier array means;
• and
• mode select means for changing the mode of operation of the apparatus between a multiplication mode where the multiplier array means implements the multiply accumulate operation and a linear interpolation mode where the multiplier array means is used to implement a linear interpolation operation between a lower limit input value and an upper limit input value based on a weighting value;
• wherein:
• when in the multiplication mode, each row of the multiplier array means is arranged such that the control input for the multiplexer means of that row is provided by an associated bit of the multiplicand value selected for that row, the first multiplexer input value is set to 0, and the second multiplexer input value is set to the multiplier value;
• when in the linear interpolation mode, each row of the multiplier array means is arranged such that the control input for the multiplexer means of that row is provided by an associated bit of the weighting value selected for that row, one of the first multiplexer input value and the second multiplexer input value is set to the lower limit input value, and other of the first multiplexer input value and the second multiplexer input value is set to the upper limit input value.