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8051 vs 8085-Difference between 8051 and 8085

This page on microcontroller 8051 vs 8085 microprocessor describes difference between 8051 and 8085. The useful links to difference between various terms are provided here.

Before we dig into 8051 vs 8085 let us understand difference between generic microcontroller vs microprocessor.

8051 Microcontroller

8051 is the microcontroller developed by Intel. Following are the features of 8051 Microcontroller:
• It houses 8 bit CPU.
• 4 KByte ROM used for code or program storage
• 128 Byte RAM to store data or variables used in program
• 32 Input/Output lines with 4 ports ( 8 lines per port)
• 2 Timers used for introducing delay and for setting the baud rate for data communication.
• 1 serial Port with one TxD and one RxD line used for serial communication with external devices.
• 6 Interrupt Sources
• Clock oscillator circuit runs at 12MHz frequency.

The figure-1 depicts 8051 microcontroller architecture. Refer 8051 Architecture➤

Microcontroller Architecture Intel 8051 core

8085 Microprocessor

8085 is the microprocessor developed by Intel. Following are the features of 8085 Microprocessor:
• It is 8 bit size processor developed as single chip using N-MOS.
• It has multiplexed address and data bus on 8 lines AD0 to AD7.
• The maximum clock frequency used in 8085 is 3 MHz.
• It has 40 pins and runs at 5V power supply.
• There are 5 hardware interrupts viz. TRAP, INTR, RST5.5, RST6.5, RST7.5
• It has about 74 programming instructions with 4 addressing modes.
• It does not house memory, but it has 16 address lines which can access 64K bytes (2^16) of externally connected memory.
• It has 8 bit lines which can address 256 (~2^8) ports connected externally.
• It has two serial lines viz. SID and SOD. These can be connected with serial peripherals.
• It consists of ACC, one flag register, 6 general purpose registers and two special registers(SP-Stack Pointer, PC-Program Counter).

The figure-2 depicts 8085 architecture. Refer 8085 Architecture➤

8085 microprocessor architecture

Following table summarizes similarities and difference between 8051 and 8085.


Specifications 8051 8085
Device Type It is a microcontroller. It is a microprocessor.
Timers/Counters YES No, Need to be connected externally.
Data bus width 8 lines 8 lines
Address Bus lines 16 16
DMA Access signals NO YES, Has HOLD and HLDA signals
Internal RAM, ROM YES No, need to be connected externally with 8085 chip, if data and code size requirement is more.
Programming 8051 programming➤ 8085 programming➤

Useful Links

Refer our Page on what a microcontroller does.
Refer our Page on microcontroller programming using C language including example.
Refer our Page on microcontroller development kit manufacturers.
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