INTERFACING TO MCS·80/8S™

PROGRAMMABLE PERIPHERAL

COMPONENTS

The MCS·85 shares with the MCS-80 a wide range of peripheral components that solve system problems and provide the designer with a great deal of flexibility in his I/O, Interrupt and DMA structures. The MCS-85 is directly com· patible with these peripherals, and, with the ex· ception of the 8257-5 DMA controller, needs no additional circuitry for their interface in a minimum system. The 8257-5 DMA controller uses an 8212 latch and some gating to support the multiplexed bus of MCS-85.

PROGRAMMABLE PERIPHERALS

The list of programmable peripherals for use with the 8085A includes:

8251A Programmable Communications

Interface

8253-5 Programmable Interval Timer

8255A-5 Programmable Peripheral Inter·

face

8257-5 Programmable DMA Controller

8259-5 Programmable Interrupt Con·

troller

8271 Diskette Controller

8273 Synchronous Data Link Con-

troller

8275 CRT Controller

8278 Keyboard/Display Controller

8279 Keyboard/Display Controller

The MCS-80/85 peripheral compatibility assures the designer. that all new peripheral com- ponents from Intel will interface to the MCS-85 bus structure to further expand the application spectrum of MCS-85.

BOB5A

BOB5A

ALE

CONTROL BUS

MEMil. lOR.

M"EMw. lOW

SERIAL I/O

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Intel MCS-80/85 manual Interfacing to MCS·80/8S Programmable Peripheral Components, Programmable Peripherals, MEMil. lOR

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.