Intel 8085

The Intel 8085 was an 8-bit microprocessor made by Intel in the mid-1970s. It was binary compatible with the more-famous Intel 8080 but required less supporting hardware, thus allowing simpler and less expensive microcomputer systems to be built.

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The "5" in the model number came from the fact that the 8085 required only a 5-volt power supply rather than the 5V and 12V supplies the 8080 needed. Both processors were sometimes used in computers running the CP/M operating system, and the 8085 later saw use as a microcontroller (much by virtue of its component count reducing feature). Both designs were later eclipsed by the compatible but more capable Zilog Z80, which took over most of the CP/M computer market as well as taking a large share of the booming home computer market in the early-to-mid-1980s.

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The 8085 can access 2^16 (= 65,536) individual 8-bit memory locations. Unlike some other microprocessors of its era, it has a separate address space for up to 2^8 (=256) I/O ports. It also has a built in register array which are usually labeled A(Accumulator),B,C,D,E,H and L, plus 16-bit Program Counter (PC) and Stack Pointer (SP), and 8-bit flag register F. The microprocessor has three hardware based interrupt operations which are found in pins 7 thru 9, these are called RST 7.5, RST 6.5, and RST 5.5 respectively. 8085 also has TRAP interrupt, which cannot be disabled, that is, TRAP is a Non-Maskable interrupt (NMI), and 8085 also has an INTR interrupt, but it's use requires an external Programmable Interrupt Controller (eg. 8259).

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The 8085 can accommodate slower memories thru externally generated Wait states (pin 35, READY), and also has provisions for Direct Memory Access (DMA) using HOLD and HLDA signals (pins 39 and 38).

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The 8085 processor has found marginal use in small scale computers up to the 21st century. The CMOS version 80C85 of the NMOS/HMOS 8085 processor has/had several manufacturers, and some versions (eg. Tundra Semiconductor Corporation's CA80C85B) have additional functionality, eg. extra machine code instructions.

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Datasheet:

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8085 datasheet

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http://eengineering.blogspot.com/

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http://www.ordersomewherechaos.com/rosso/fetish/m102/web100/docs/intel-8085-preface.html

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