The RCA CDP1861 was an integrated circuit

Video Display Controller A video display controller or VDC (also called a display engine or display interface) is an integrated circuit which is the main component in a video-signal generator, a device responsible for the production of a TV video signal in a computing ...

, released by the

Radio Corporation of America The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...

(RCA) in the mid-1970s as a support chip for the

RCA 1802 The COSMAC (Complementary Symmetry Monolithic Array Computer) is an 8-bit microprocessor family introduced by RCA. It is historically notable as the first CMOS microprocessor. The first production model was the two-chip CDP1801R and CDP1801U, w ...

microprocessor. The chip cost in 1977 amounted to less than US$20.

History

The CDP1861 was manufactured in a low-power

CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSFE ...

technology, came in a 24-pin DIP (

Dual in-line package In microelectronics, a dual in-line package (DIP or DIL), is an electronic component package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole mounted to a printed circuit board (P ...

), and required a minimum of external components to work. In 1802-based microcomputers, the CDP1861 (for the

NTSC The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...

video format, CDP1864 variant for

PAL Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...

), used the 1802's built-in DMA controller to display black and white (monochrome)

bitmap In computing, a bitmap is a mapping from some domain (for example, a range of integers) to bits. It is also called a bit array A bit array (also known as bitmask, bit map, bit set, bit string, or bit vector) is an array data structure that c ...

ped graphics on standard TV screens. The CDP1861 was also known as the Pixie graphics system, display, chip, and video generator, especially when used with the COSMAC ELF microcomputer. Other known chip markings for the 1861 are TA10171, TA10171V1 and a TA10171X, which were early designations for "pre-qualification engineering samples" and "preliminary part numbers", although they have been found in production

RCA Studio II The RCA Studio II is a home video game console made by RCA that debuted in January 1977. The graphics of Studio II games were black and white and resembled those of earlier Pong consoles and their clones. The Studio II also did not have joysticks ...

game consoles and Netronics Elf microcomputers. The CDP1861 was also used in the

Telmac 1800 The Telmac 1800 was an early microcomputer delivered in kit form. It was introduced in 1977 by Telercas Oy, the Finland, Finnish importer of RCA microchips. Most of the 2,000 kits manufactured over four years were bought by electronics enthusia ...

and Oscom Nano microcomputers.

Specifications

The 1861 chip could display 64

pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the smal ...

s horizontally and 128 pixels vertically, though by reloading the 1802's R0 DMA (

direct memory access Direct memory access (DMA) is a feature of computer systems and allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU). Without DMA, when the CPU is using programmed input/output, it is t ...

) register via the required 1802 software controller program and interrupt service routine, the resolution could be reduced to 64×64 or 64×32 to use less memory than the 1024 bytes needed for the highest resolution (with each monochrome pixel occupying one bit) or to display square pixels. A resolution of 64×32 created square pixels and used 256 bytes of memory (2K bits). This was the usual resolution for the

Chip-8 CHIP-8 is an interpreted programming language, developed by Joseph Weisbecker made on his 1802 Microprocessor. It was initially used on the COSMAC VIP and Telmac 1800 8-bit microcomputers in the mid-1970s. CHIP-8 programs are run on a CHIP-8 ...

game programming system. Since the video graphics frame buffer was often similar or equal in size to the memory size, it was not unusual to display your program/data on the screen allowing you to watch the computer "think" (i.e. process its data). Programs which ran amok and accidentally overwrote themselves could be spectacular. The CDP1862 Color Generator Circuit IC, an 1861 companion chip, could be used to generate limited color graphics. Due to the discontinuation of the 1861 and its rarity, in 2004 a fully functional analogue called the Spare Time Gizmos STG1861 was made for use with the newly designed and produced ELF 2000 (Elf2K) computer.Elf 2000 Accessories
/ref> It is made in the form of a small

printed circuit board A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in Electrical engineering, electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a L ...

(PCB) with two small

programmable logic device A programmable logic device (PLD) is an electronic component used to build reconfigurable digital circuits. Unlike digital logic constructed using discrete logic gates with fixed functions, a PLD has an undefined function at the time of manuf ...

s, two simple TTL chips, and a 24-pin DIP connector for mounting in place of the original chip.

History

Specifications

Gallery

References

External links