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Unit 3: Assembly Language Programming of 8085

• Describe Instruction Set Classification Notes

• Discuss Instruction Format
• Understand Programming

Introduction

Intel 8085 microprocessor is the next generation of Intel 8080 CPU family. In addition to being
faster than the 8080, the 8085 had the following enhancements:
• Intel 8085 had single 5 Volt power supply.

• Clock oscillator and system controller were integrated on the chip.
• The CPU included serial I/O port.
• Two new instructions were added to 8085 instruction set.

The CPU also included a few undocumented instructions. These instructions were supposed to
be a part of the CPU instruction set, but at the last moment they were left undocumented because
they were not compatible with forthcoming Intel 8086.
Unlike the other programming languages catalogued here, assembly language is not a single
language, but rather a group of languages. Each processor family (and sometimes individual
processors within a processor family) has its own assembly language.
In contrast to high level languages, data structures and program structures in assembly language
are created by directly implementing them on the underlying hardware. So, instead of cataloguing
the data structures and program structures that can be built (in assembly language you can build
any structures you so desire, including new structures nobody else has ever created), we will
compare and contrast the hardware capabilities of various processor families.

3.1 The 8085 Programming Model
The 8085 programming model includes six registers, one accumulator, and one flag register, as
shown in Figure 3.1. In addition, it has two 16-bit registers: the stack pointer and the program
counter. They are described briefly as follows:

Figure 3.1: 8085 Programming Model

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