A 3μ CMOS Digital Codec with Programmable Echo Cancellation and Gain Setting

A 3μ CMOS Digital Signal Processor (DSP) performs speech signal shaping, programmable echo cancellation and gain setting functions for telephone application. A/D and D/A conversions are performed by making use of ΔΣ modulators, decimator and interpolator filter blocks. In addition, the DSP acts as a control interface between the SLIC and the line card controller, the debouncing of eight line status bits included.