The NEC μPD7720 is the name of fixed point digital signal processors from

NEC is a Japanese multinational information technology and electronics corporation, headquartered in Minato, Tokyo. The company was known as the Nippon Electric Company, Limited, before rebranding in 1983 as NEC. It provides IT and network soluti ...

(currently

Renesas Electronics is a Japanese semiconductor manufacturer headquartered in Tokyo, Japan, initially incorporated in 2002 as Renesas Technology, the consolidated entity of the semiconductor units of Hitachi and Mitsubishi excluding their dynamic random-access ...

). Announced in 1980, it became, along with the

Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globa ...

TMS32010, one of the most popular DSPs of its day.

Background

In the late 1970s, telephone engineers were attempting to create technology with sufficient performance to enable digital touch-tone dialing. Existing digital signal processing solutions required over a hundred chips and consumed significant amounts of power.

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 seri ...

responded to this potential market by introducing the Intel 2920, an integrated processor that, while it had both digital-to-analog and analog-to-digital converters, lacked additional features (such as a hardware multiplier) that would be found in later processors. Announcements for the first "real" DSPs, the NEC μPD7720 and the Bell Labs DSP-1 chip, occurred the following year at the 1980

IEEE The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operat ...

International Solid-State Circuits conference. The μPD7720 first became available in 1981 and commercially available in late 1982 at a cost of US$600 each (approx. $ today). Beyond their initial use in telephony, these processors found applications in disk drive and graphics controllers, speech synthesis and modems.

Architecture

Detailed descriptions of the μPD7720 architecture are found in Chance (1990), Sweitzer (1984) and Simpson (1984). Briefly, the NEC μPD7720 runs at 4 MHz frequency with 128-word data RAM, 512-word data ROM, and 512-word program memory, which has

VLIW Very long instruction word (VLIW) refers to instruction set architectures designed to exploit instruction level parallelism (ILP). Whereas conventional central processing units (CPU, processor) mostly allow programs to specify instructions to exe ...

-like instruction format, enabling all of ALU operation, address register increment/decrement operation, and move operation in one cycle.

Variants

The NEC μPD77C25, which succeeded the μPD7720, runs at 8 MHz frequency with 256-word data RAM, 1,024-word data ROM, and 2,048-word program memory.

References

External links

* Datasheets for the UPD7720A, UPD7720AC and UPD7720AD are availabl
here
{{Renesas Electronics muPD07720 Digital signal processors