﻿ RCA1802


The Radio Corporation of America (RCA ) gave 1974 as a first RCA 1802 CMOS microprocessor on the market. It can be operated with an operating voltage of up to 10 V and a frequency of a maximum of 6.4 MHz. At low voltages correspondingly less. The internal structure and the instructions are very simple.


From the beginning of 1802 was made ​​as the Silicon -on- Sapphire version. This design gave the microprocessor a certain degree of resistance to radiation and electrostatic discharge. Together with its ability to operate at extremely low voltages, this made the 1802 very suitable for space travel ( were In addition to this time very few, if any, processors on the market which were similar insensitive to radiation). The 1802 was used in the Galileo mission of NASA and was a popular microprocessor for satellites.

A number of microcomputers based on the 1802, including the COSMAC ELF, COSMAC VIP, ELF II, SuperELF and the Yugoslav Pecom 32, as well as the RCA Studio II game console. In the chess computer world of 1802 came in the early 1980s in Mephisto I, II and Mephisto Mephisto III of the Munich-based electronics manufacturer Hegener & Glaser used.

Internal structure

Data bus width of 8 bits Address bus width 16 bit multiplexed I / O addresses 7

Next to the accumulator, the processor has sixteen 16 -bit registers, which can also be used achtbitweise. There are two registers ( X, P ) with four bits, which specify which work the 16- bit register as a data pointer and Program Counter. There is only one carry flag to battery. A zero flag is not required. There is an output signal that can be set programmatically. Four EF- lines can be queried by the program. The address bus is multiplexed as two sets of eight bits. The cycle time is one-eighth of the clock frequency. Almost all commands need two, just three cycles.

Command structure

The simple design of the hardware continues with the program commands.

For example, it takes 4 commands to load one of the 16 registers:

-------------------------------------------------- ---------------------------------------    LDI n1; LOAD IMMEDIATE 1st byte in the battery    PLO 1; PUT LOW battery content in the low byte of register R1    LDI n2; LOAD immidiate 2nd byte into the accumulator    PHI 1; PUT HIGH the battery capacity in the high-order byte of the register R1 There are also branch instructions which, although only need 2 cycles and 2 bytes, but their aim within the same page, ie the higher 8 bits of the address are not allowed to change. A direct subroutine call (CALL ), there is not a similar function can be achieved by changing the program counter.


In the novel, the final boss: extra lives Part III of Constantin Gillies the CPU features concerning radiation resistance and use in the early space are processed belletristic.