RF8051 vs 8085: Key Differences Explained
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The 8051, developed by Intel in 1980, is an 8-bit microcontroller designed for embedded applications. It belongs to the MCS-51 family of microcontrollers and has gained widespread adoption due to its versatility and ease of use.
The 8085, introduced by Intel in 1976, is an 8-bit microprocessor primarily used for educational purposes and simple control applications. It belongs to the 8-bit microprocessor family and is recognized for its simplicity and ease of understanding.
Features of the 8051 Microcontroller
The 8051 microcontroller, developed by Intel, boasts the following features:
- 8-bit CPU
- 4 KB ROM for program storage
- 128 Byte RAM for data storage
- 32 Input/Output lines with 4 ports (8 lines per port)
- 2 Timers for introducing delays and setting baud rates for data communication
- 1 Serial Port with TxD and RxD lines for serial communication with external devices
- 6 Interrupt Sources
- Clock oscillator circuit runs at 12MHz frequency
Figure 1: 8051 Microcontroller Architecture
Features of the 8085 Microprocessor
The 8085 microprocessor, developed by Intel, offers the following features:
- 8-bit processor built as a single chip using N-MOS technology
- Multiplexed address and data bus on 8 lines (AD0 to AD7)
- Maximum clock frequency of 3 MHz
- 40 pins and runs at 5V power supply
- 5 hardware interrupts: TRAP, INTR, RST5.5, RST6.5, RST7.5
- Approximately 74 programming instructions with 4 addressing modes
- No internal memory; 16 address lines can access 64K bytes (2^16) of externally connected memory
- 8-bit lines can address 256 (~2^8) ports connected externally
- Two serial lines: SID and SOD, for connection with serial peripherals
- Consists of ACC, one flag register, 6 general-purpose registers, and two special registers (SP-Stack Pointer, PC-Program Counter)
Figure 2: 8085 Architecture
Difference Between 8051 and 8085
The following table summarizes the similarities and differences between the 8051 and 8085:
| Specifications | 8051 | 8085 |
|---|---|---|
| Architecture | Harvard architecture | Von Neumann architecture |
| Data Bus Width | 8-bit | 8-bit |
| Address Bus Width | 16-bit | 16-bit |
| Program Memory | Internal ROM (Up to 4 KB) | External ROM |
| RAM | Internal RAM (128 bytes) | External RAM |
| Clock Speed | Up to 24 MHz | 3 MHz to 6 MHz |
| Instruction set | Complex (Includes bit, byte, and block operations) | Simple |
| Timers/Counters | 2 or more (depending on the variant) | None (requires external peripherals) |
| I/O Ports | 4 ports (32 I/O lines) | None (requires external peripherals) |
| Serial Communication | Built-in UART | None (requires external peripherals) |
| Interrupts | 5 interrupt sources | 5 interrupt sources |
| Power Consumption | Low power consumption | Relatively higher power consumption |
| DMA Access signals | NO | YES, Has HOLD and HLDA signals |
| Peripheral Interfaces | Built-in support for I2C, SPI, and more | Requires external interfacing ICs |
| Development Ease | Easier with more integrated peripherals | More complex, requires additional components |
| Applications | Embedded systems, automotive, consumer electronics | Basic computing, control systems |
Conclusion
The 8051 microcontroller and the 8085 microprocessor serve different purposes and are designed with different architectures. The 8051, with its integrated peripherals and ease of development, is better suited for modern embedded systems. In contrast, the 8085 is typically used in educational settings and simpler control applications. Understanding their differences is key to choosing the right microcontroller for a specific application.
