INTERFACING TO STANDARD MEMORY

The MC5-85 was designed to support the full range of system configurations from small 3 chip applications to large memory and 110 ap- plications. The 8085A CPU issues advanced READIWRITE status signals (SO, 51, and 101M) so that, in the case of large systems, these signals could be used to simplify bus arbitra- tion logic and dynamic RAM refresh circuitry.

In large, memory-intensive systems, standard memory devices may provide a more cost- effective solution than do the special 8155 and 8355 devices, especially where few 110 lines are required.

DEMULTIPLEXING THE BUS

In order to interface standard memory com- ponents such as Intel® 2114,2142,2716, 2316E, 2104A and 2117 the MeS-85 bus must be "demultiplexed". This is accomplished by con- necting an Intel® 8212 latch to the data bus and strobing the latch with the ALE signal from the 8085A CPU. The ALE signal is issued to indicate that the multiplexed bus contains the lower 8-bits of the address. The 8212 latches this in- formation so that a full 16-bit address is available to interface standard memory com- ponents.

USE OF 8212

Larg~, memory intensive systems are usually multi-card implementations and require some form of TIL buffering to provide necessary cur- rent and voltage levels. Frequently, 8212s are used for this purpose. The 8212 has the advan- tage of being able to latch and demultiplex the address bus and provide extra address drive capability at the same time.

BOBSA

ALE

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Intel MCS-80/85 manual Interfacing to Standard Memory, Demultiplexing the BUS
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MCS-80/85 specifications

The Intel MCS-80/85 family, introduced in the late 1970s, is a seminal collection of microprocessors that played a pivotal role in the early days of computing. The MCS-80 series, initially targeting embedded systems and control applications, gained remarkable attention due to its innovative architecture and flexible programming capabilities.

The MCS-80 family is anchored by the 8080 microprocessor, which was one of the first fully integrated 8-bit microprocessors. Released in 1974, the 8080 operated at clock speeds ranging from 2 MHz to 3 MHz and featured a 16-bit address bus capable of addressing up to 64KB of memory. The processor’s instruction set included around 78 instructions, providing extensive capabilities for data manipulation, logic operations, and branching.

Complementing the 8080 was a suite of support chips, forming the MCS-80 platform. The most notable among them was the 8155, which integrated a static RAM, I/O ports, and a timer, tailored for ease of designing systems around the 8080. Other support chips included the 8085, which provided improvements with an integrated clock generator, making it compatible with more modern designs and applications.

The MCS-85 series, on the other hand, revolves around the 8085 microprocessor, which provided a more advanced architecture. The 8085 operated at clock speeds of up to 6 MHz and came with a 16-bit address bus, similar to its predecessor. However, it introduced more sophisticated features, including an enhanced instruction set and support for interrupt-driven programming. These enhancements made the 8085 especially appealing to developers working in real-time processing environments.

The MCS-80/85 family utilized NMOS technology, known for its lower power consumption and higher performance compared to previous technologies like TTL. The family’s architecture allowed for easy interfacing with a variety of peripherals, making it a favorite for educational institutions and hobbyists embarking on computer engineering projects.

With its robustness, versatility, and affordability, the Intel MCS-80/85 microprocessors laid the groundwork for many subsequent microcomputer systems and applications. The legacy of this powerful family continues to influence modern microprocessor design, emphasizing the importance of reliable architecture in a rapidly evolving technology landscape.
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