The IDT821024 is a single-chip, four channel PCM CODEC with onchip filters. The device provides analog-to-digital and digital-to-analog conversions and supports both a-law and -law companding. The digital filters in IDT821024 provides the necessary transmit and receive filtering for voice telephone circuit to interface with time-division multiplexed systems. All of the digital filters are performed in digital signal processors operating from an internal clock, which is derived from MCLK. The fixed filters set the transmit and receive gain and frequency response. In the IDT821024 the PCM data is transmitted to and received from the PCM highway in time slots determined by the individual Frame Sync signals (FSRn and FSXn, where n = 1-4) at rates from 256 KHz to 8.192 MHz. Both Long and Short Frame Sync modes are available in the IDT821024.