Page 84 - DCAP210_INTRODUCTION__TO_MICROPROCESSORS

Introduction to Microprocessors

Notes The address and data bus are multiplexed in this processor which helps in providing more control
signals. 8085 microprocessor has 1 Non-maskable interrupt and 3 maskable interrupts. It provides
serial interfacing with serial input data (SID) and serial output data (SOD).
It has a set of registers for performing various operations. The various registers include:
• Accumulator (register A)
• Registers: B, C, D, E, H and L

6.1 The 8085 Architecture

The 8085 is an 8-bit microprocessor. This design is the enhanced design of the earlier
microprocessor 8080, which had three operating voltages and data lines/address lines
independent. In 8085 the bus structure is multiplexed with 8 lower address lines and requires
only 5 V as single power supply. The external chips for clock generation and control system in
8080 are not available in 8085 microprocessor these are designed using IVMOS technology. The
operating clock frequency for 8085 is faster than the 8080. The operating clock frequencies further
high for enhanced versions 8085 AH which is designed using the HMOS technology, the operating
frequency is from 3 MHz to 6 MHz.
All the signals can be classified into six groups:
1. Address bus
2. Data bus
3. Control and status signals
4. Power supply and frequency signals
5. Externally initiated signals
6. Serial I/O ports.

6.1.1 The 8085 Pin Diagram

Figure 6.1: 8085 Microprocessor pinout and signals

6.1.2 Pin Details

The 8085A (commonly known as 8085) is an8-bit general purpose microprocessor capable of
addressing 64k of memory and consist of approximately 6200 transistors. It is the most popular

78 LOVELY PROFESSIONAL UNIVERSITY