The 8085 is a 8 bit microprocessor from Intel. All the data buses and almost all the registers in the processor are of 8 bits.
But the 8 bit processors have their limitations:
- In 8 bit microprocessor, microprocessor can perform any arithmetic and logical operation only on 8 bit data at a time. For multi-byte numbers, microprocessor takes more time, as ALU is 8 bit.
- Due to the 16 bit address lines, we can address only up to 64 KB of memory, so we cannot use Intel 8085 in IBM Standard PC. Because, in IBM architecture standard, minimum 640KB of memory is required.
- 8085 has multiplexed address and data bus, so extra hardware is required to separate address signals from the data signals.
- Flags register has limited flags.
- Interrupts are very limited in 8085. Normally in larger microprocessor based system, more interrupts are present.
- Operating frequency is less, so the speed of execution is slow.
- While reading or writing 16 bit or more bytes of data from the memory or I/O device, the microprocessor needs more operation cycles.
- Using 8085, we cannot design multi-processor system.
- Due to limited 8 bit size of the all registers, we can store limited data bytes in the microprocessor memory.
For overcoming these limitations micro-processor with wider data buses and higher capacity registers were developed
