RCA 1802

Domain	Definition
Computing	RCA 1802 An extremely simple microprocessor fabricated in CMOS, which allowed it to run at 6.4 MHz (at 10V, but very fast for 1974) or suspended with the clock stopped. It was an 8 bit processor, with 16-bit addressing but the major features were its extreme simplicity, and the flexibility of its large register set. Simplicity was the primary design goal, and in that sense it was one of the first RISC chips. It had sixteen 16-bit registers, which could be accessed as thirty-two 8-bit registers, and an accumulator D used for arithmetic and memory access - memory to D, then D to registers and vice versa, using one 16-bit register as an address. This led to one person describing the 1802 as having 32 bytes of RAM and 65535 I/O ports. A 4-bit control register P selected any one general register as the program counter, while control registers X and N selected registers for I/O Index and the operand for the current instruction. All instructions were 8 bits - a 4-bit op code (total of 16 operations) and 4-bit operand register stored in N. There was no real conditional branching, no subroutine support and no actual stack but clever use of the register set allowed these to be implemented - for example, changing P to another register allowed jump to a subroutine. Similarly, on an interrupt P and X were saved, then R1 and R2 were selected for P and X until an RTI restored them. The RCA 1805 was an enhanced version. Apart from the COSMAC (VIP?) microcomputer kit, the 1802 saw action in some video games from RCA and Radio Shack. It was used in the DREAM 6800 and ETI-660 computers and is also the heart of the Voyager, Viking and Galileo probes. One reason for this is that the 1802 was also fabricated on sapphire (Silicon on Sapphire), which leads to radiation and static resistance, ideal for space operation. (1994-11-16). Source: The Free On-line Dictionary of Computing.
Source: compiled by the editor from various references; see credits.

Anagrams: RCA 1802

Scrabble® Enable2K-Verified Anagrams
	Words within the letters "0-1-2-8-a-c-r"
	-4 letters: arc, car.
	-5 letters: ar.
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