In-memory computation system with built-in subtraction mode for handling matrix vector multiplication of signed feature data and signed computational weight data

Abstract

An in-memory computation circuit includes a memory array with memory cells arranged in a matrix in rows and columns. Groups of memory cells store computational weights for an in-memory compute (IMC) operation that is performed with a first multiply and accumulate (MAC) elaboration to produce a first analog signal and a second MAC elaboration to produce a second analog signal. An analog-to-digital converter circuit operates to: increment a count value in a counter circuit in response to the first analog signal; convert the count value in the counter circuit to a negated count value; and increment the count value in the counter circuit starting from the negated count value in response to the second analog signal.