Zilog Z80

The Zilog Z80 is an 8-bit microprocessor designed and manufactured by Zilog. It was launched in July 1976 and was widely used in both desktop computers and embedded systems, including military applications. The Z80 and its derivatives were one of the most commonly used CPUs of all time, and, along with the MOS Technology 6502 family, dominated the eight-bit microcomputer market from the late 1970s to the mid-1980s.

Zilog licensed the Z80 design to several vendors, though many East European (for instance, Russian) manufacturers made unlicensed copies. This enabled a small company's product to gain acceptance in the world market since second sources from far larger companies such as Toshiba started to manufacture the device. Consequently, Zilog has made less than 50% of the Z80s since its conception. In recent decades Zilog has refocused on the ever-growing market for embedded systems (for which the original Z80 and the Z180 were designed) and the most recent Z80-compatible microcontroller family, the fully pipelined 24-bit eZ80 with a linear 16 MB address range, has been successfully introduced alongside the simpler Z180 and Z80 products.

NEC

NEC Corporation (日本電気株式会社, Nippon Denki Kabushiki Gaisha) is a Japanese multinational provider of information technology (IT) services and products, with its headquarters in Minato, Tokyo, Japan. NEC provides IT and network solutions to business enterprises, communications services providers and to government agencies, and has also been the biggest PC vendor in Japan since the 1980s. The company was known as the Nippon Electric Company, Limited, before rebranding in 1983 as just NEC. Its NEC Semiconductors business unit was one of the worldwide top 20 semiconductor sales leaders before merging with Renesas Electronics. NEC is a member of the Sumitomo Group.

History

1898 to 1919

Kunihiko Iwadare and Takeshiro Maeda established Nippon Electric Limited Partnership on August 31, 1898 by using facilities that they had bought from Miyoshi Electrical Manufacturing Company. Iwadare acted as the representative partner; Maeda handled company sales. Western Electric, which had an interest in the Japanese phone market, was represented by Walter Tenney Carleton. Carleton was also responsible for the renovation of the Miyoshi facilities. It was agreed that the partnership would be reorganized as a joint-stock company when treaty would allow it. On July 17, 1899 the revised treaty between Japan and the United States went into effect. Nippon Electric Company, Limited was organized the same day with Western Electric Company to become the first Japanese joint-venture with foreign capital. Iwadare was named managing director. Ernest Clement and Carleton were named as directors. Maeda and Mototeru Fujii were assigned to be auditors. Iwadare, Maeda and Carleton handled the overall management.

Floppy-disk controller

A floppy-disk controller (FDC) is a special-purpose chip and associated disk controller circuitry that directs and controls reading from and writing to a computer's floppy disk drive (FDD). This article contains concepts common to FDCs based on the NEC µPD765 and Intel 8272A or 82072A and their descendants, as used in the IBM PC and compatibles from the 1980s and 1990s. The concepts may or may not be applicable to, or illustrative of, other controllers or architectures.

Overview

A single floppy-disc controller (FDC) board can support up to four floppy disk drives. The controller is linked to the system bus of the computer and appears as a set of I/O ports to the CPU. It is often also connected to a channel of the DMA controller. On the x86 PC the floppy controller uses IRQ 6, on other systems other interrupt schemes may be used. The floppy disc controller usually performs data transmission in direct memory access (DMA) mode.

The diagram below shows a floppy disc controller which communicates with the CPU via an Industry Standard Architecture (ISA) bus. An alternative arrangement which is more usual in recent designs has the FDC included in a super I/O chip which communicates via a Low Pin Count (LPC) bus.

Numerical Electromagnetics Code

The Numerical Electromagnetics Code, or NEC, is a popular antenna modeling system for wire and surface antennas. It was originally written in FORTRAN in the 1970s by Gerald Burke and Andrew Poggio of the Lawrence Livermore National Laboratory. The code was made publicly available for general use and has subsequently been distributed for many computer platforms from mainframes to PCs.

NEC is widely used for modelling antenna designs, particularly for common designs like television and radio antennas, shortwave and ham radio, and similar examples. Examples of practically any common antenna type can be found in NEC format on the internet. While highly adaptable, NEC has its limits, and other systems are commonly used for very large or complex antennas, or special cases like microwave antennas.

By far the most common version is NEC-2, the last to be released in fully public form. There is a wide and varied market of applications that embed the NEC-2 code within frameworks to simplify or automate common tasks. Later versions, NEC-3 and NEC-4, are freely available as compiled binaries but have not been nearly as popular.