Implementation of the PCM interface for the 60-channel TMUX with MH89790

Abstract

The 60-channel TDM-FDM transmultiplexer (TMUX) provides bi-directional conversion between PCM and FDM signals. It converts one FDM standard supergroup of 60 channels, in the frequency band 312 to 552 kHz, into two PCM streams of 2048 kbit/s, each of which carries 30 speech channels. The PCM interface of the 60-channel TMUX receives two HDB3 2048 kbit/s PCM line inputs and converts them into two serial linear two's complement format. In addition, it monitors (or transmits) PCM alarm information and detects (or inserts) signalling A, B, C and D bits. Since the functions of the PCM interface are very complex, in order to reduce the complexity, enhance the stability and the reliability of the circuit, the authors use the LSI chip MH89790 as the main chip to realize the functions of the interface.<>