RCA 1802

(processor)An extremely simple microprocessor fabricated inCMOS, running at 6.4 MHz at 10V (very fast for 1974). Itcould be suspended with the clock stopped. It was an 8-bitprocessor, with 16-bit addressing. Simplicity was the primarydesign goal, and in that sense it was one of the first RISCchips. It had sixteen 16-bit registers, which could beaccessed as thirty-two 8-bit registers, and an accumulator Dused for arithmetic and memory access - memory to D, then D toregisters and vice versa, using one 16-bit register as anaddress. This led to one person describing the 1802 as having32 bytes of RAM and 65535 I/O ports. A 4-bit controlregister P selected any one general register as the program counter, while control registers X and N selected registersfor I/O Index and the operand for the current instruction.All instructions were 8 bits - a 4-bit op code (total of 16operations) and 4-bit operand register stored in N. Therewas no real conditional branching, no subroutine supportand no actual stack but these could be implemented by cleveruse of registers, e.g. changing P to another register allowedjump to a subroutine. Similarly, on an interrupt P and X weresaved, then R1 and R2 were selected for P and X until an RTIrestored them.

The RCA 1805 was an enhanced version.

The 1802 was used in the COSMAC (VIP?) microcomputer kit,some video games from RCA and Radio Shack, and theETI-660 computer. It was chosen for the Voyager, Viking andGalileo space probes as it was also fabricated in Silicon on Sapphire, giving radiation and static resistance, ideal forspace operation.

More history.

单词	rca 1802
释义	RCA 1802 RCA 1802 (processor)An extremely simple microprocessor fabricated inCMOS, running at 6.4 MHz at 10V (very fast for 1974). Itcould be suspended with the clock stopped. It was an 8-bitprocessor, with 16-bit addressing. Simplicity was the primarydesign goal, and in that sense it was one of the first RISCchips. It had sixteen 16-bit registers, which could beaccessed as thirty-two 8-bit registers, and an accumulator Dused for arithmetic and memory access - memory to D, then D toregisters and vice versa, using one 16-bit register as anaddress. This led to one person describing the 1802 as having32 bytes of RAM and 65535 I/O ports. A 4-bit controlregister P selected any one general register as the program counter, while control registers X and N selected registersfor I/O Index and the operand for the current instruction.All instructions were 8 bits - a 4-bit op code (total of 16operations) and 4-bit operand register stored in N. Therewas no real conditional branching, no subroutine supportand no actual stack but these could be implemented by cleveruse of registers, e.g. changing P to another register allowedjump to a subroutine. Similarly, on an interrupt P and X weresaved, then R1 and R2 were selected for P and X until an RTIrestored them. The RCA 1805 was an enhanced version. The 1802 was used in the COSMAC (VIP?) microcomputer kit,some video games from RCA and Radio Shack, and theETI-660 computer. It was chosen for the Voyager, Viking andGalileo space probes as it was also fabricated in Silicon on Sapphire, giving radiation and static resistance, ideal forspace operation. More history.
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