Combined digital write and analog rewrite process for non-volatile memory

Abstract

A non-volatile memory stores both analog and digital information in an array, and has digital and analog read and write circuits and dual I/O interfaces which allow input and output signals in digital or analog form. A user selects the input signal, output signal, and data storage formats. Each selection can be digital or analog format. On-chip analog-to-digital and digital-to-analog converters allow conversion of signals from one format into another. Analog signals can be read or written serially, and one embodiment includes an address counter and an internal oscillator for generating sequential addresses. An output amplifier for driving a speaker and an input amplifier for a microphone allow stored sounds to be directly recorded and reproduced. A real-time recording method in accordance with an embodiment of the invention writes digital samples to the memory using a fast digital write circuit while data is being acquired. The stored digital values are subsequently read, converted to analog form using an internal converter, and rewritten in analog form in the memory using a slower analog write circuit. The reading, converting and rewriting can be conducted entirely within the memory.