LSI Processor for Digital Signal Processing and Its Application to 4800 Bit/s Modem

This paper describes a fast data processing LSI unit tailored to the digital signal processing (DSP) applications in the field of electrical communications. The results of successful application to the 4800 bit/s modem are also given. The LSI processor discussed here adopts a firmware control scheme to enhance the flexibility and freedom of application and extensively utilizes the pipeline processing technique to attain high speed data handling capability. The various operations encountered in DSP systems are unified into one operation of the type and the LSI processor is designed to continuously perform this operation, while the data to be operated are transferred sequentially into the processor controlled by exterior firmware. The developed LSI handles 8 bit data at the clock frequency of 1.152 MHz and manages 144 K operations per second (6.9 μs cycle time). The LSI is an N-MOS chip containing 1500 gates and packaged in a 40 pin DIP. The automatic equalizer for 4800 bit/s modem was implemented using two of the developed LSI processors and about 4 K ROM and 1 K RAM memory chips. The measurement on this modem gave the error rate of 10^-5at dB and error free phase jitter allowance of 55° p-p. Application of the LSI processor to digital filters for roll-off spectrum shaping and timing signal extraction is also described.