For the technical portion of the Wireless PSI exam, basic digital electronics is a core pillar. Among all electronic topics, the comparison between Microprocessors (like the 8085) and Microcontrollers (like the 8051) is a frequent source of questions.
Let us break down their fundamental architectural differences, storage systems, and computational properties.
1. Structural Differences
The primary difference lies in integration. A microprocessor is purely a central processing unit (CPU). It does not contain memory or input/output ports on the chip itself.
Conversely, a microcontroller is a complete microcomputer built on a single silicon chip. It integrates the CPU, RAM, ROM, timers, and I/O pins all together.
- Microprocessor (8085): Requires external RAM (like 6264) and external ROM (like 2764) for operations.
- Microcontroller (8051): Contains built-in 128 bytes of RAM and 4KB of flash ROM.
2. Application and Power Requirements
Because microprocessors are general-purpose, they are designed for complex, high-power calculations. They run at high clock frequencies (often in GHz) and draw substantial power.
Microcontrollers are designed for highly specific tasks (like controlling an AC or washing machine). They run at lower clock rates (mostly in MHz), are extremely energy-efficient, and have robust power-saving modes.
Microprocessors generally use Von Neumann architecture (unified storage for data and program instructions), while microcontrollers often use Harvard architecture (separate memory space for code and data).
3. Typical Exam Questions
Expect questions regarding the size of the data bus and address bus of the 8085 (8-bit data bus, 16-bit address bus) and the function of standard control pins such as ALE (Address Latch Enable) and IO/M.