Microprocessor & Interfaces

Subject: Microprocessor & Interfaces  Course Objectives: 1. To introduce the architecture, interfacing and programming of 8085 microprocessor and various peripheral interfacing devices. Unit - 1 Microprocessor Architecture Introduction to Microprocessors, Architecture of 8085, Pin Configuration and Function; internal register & flag register, Generation of Control Signals: Bus Timings: Demultiplexing of address / data bus; Fetch Cycle, Execute Cycle, Instruction Cycle, struction Timings and Operation Status, Timing Diagram. Unit - 2 Instructions Set and Programming With 8085 Instruction for Data Transfer. Arithmetic and Logical Operations. Branching Operation: Machine Cycle Concept; Addressing Modes; Instructions Format: Stacks. Subroutine and Related Instructions. Elementary Concepts of Assemblers, Assembler Directives, Looping and Counting: Software Counters with Time Delays: Simple Programs using Instruction Set of 8085: Debugging: Programs Involving Subroutines. Program...

Demultiplexing Address/Data Bus AD7- AD0  Pin 30 of 8085 is the ALE pin which stands for ‘Address Latch Enable’. ALE signal is used to demultiplex the lower order address bus (AD0 – AD7). Pins 12 to 19 of 8085 are AD0 – AD7 which is the multiplexed address-data bus. Multiplexing is done to reduce the number of pins of 8085. Lower byte of address (A0 – A7) are available from AD0 – AD7 (pins 12 to 19) during T1 of machine cycle. But the lower byte of address (A0 – A7), along with the upper byte A8 – A15 (pins 21 to 28) must be available during T2 and rest of the machine cycle to access memory location or I/O ports. Now ALE signal goes high at the beginning of T1 of each machine cycle and goes low at the end of T1 and remains low during the rest of the machine cycle. This high to low transition of ALE signal at the end of T1 is used to latch the lower order address byte (A0 – A7) by the latch IC 74LS373, so that the lower byte A0 – A7 is continued to be available till the end of the m...

  Instruction Format An  instruction  is a command to the microprocessor to perform a given task on a specified data. Each instruction has two parts: one is task to be performed, called the  operation code  (opcode), and the second is the data to be operated on, called the  operand.  The operand (or data) can be specified in various ways. It may include 8-bit (or 16-bit ) data, an internal register, a memory location, or 8-bit (or 16-bit) address. In some instructions, the operand is implicit. Instruction word size The 8085 instruction set is classified into the following three groups according to word size: 1.        One-word or 1-byte instructions 2.        Two-word or 2-byte instructions 3.        Three-word or 3-byte instructions In the 8085, "byte" and "word" are synonymous because it is an 8-bit microprocessor. However, instructions are commonly referred to ...

  Instruction Set of 8085 An  instruction  is a binary pattern designed inside a microprocessor to perform a specific function. The entire group of instructions, called the  instruction set , determines what functions the microprocessor can perform. These instructions can be classified into the following five functional categories: data transfer (copy)  operations, arithmetic operations, logical operations, branching operations, and machine-control operations. Data Transfer (Copy) Operations This group of instructions copy data from a location called a source to another location called a destination, without modifying the contents of the source. In technical manuals, the term  data transfer  is used for this copying function. However, the term  transfer  is misleading; it creates the impression that the contents of the source are destroyed when, in fact, the contents are retained without any modification. The various types of data transf...