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• 1. Microprocessor and Memory Basics
• What is a microprocessor and where are they used?
• Abstract system architecture
• System communication
  • Data bus, address bus, control bus
  • Reading data from memory
  • Writing data to memory
  • The Address Capacity of Memory
• Inside the microprocessor
  • The Arithmetic and Logic Unit
  • The Program Counter
  • Registers
• Inside memory
  • Memory Read and Write Operations
  • Calculating storage space
  • Address decoders
  • Tri-state buffers
  • Multiple memory chips
  • Other types of memory
  • Memory mapped input/output

Memory mapped input/output

We want to create input and output ports that each appear to the microprocessor just like a location in memory (enabling the microprocessor to interact with the outside world).

This would enable us to arrange that every byte read from the input port was a character read from the keyboard, and every byte written appeared as a character on the monitor screen.

The diagram shows an input port and an output port both mapped to memory location 00000000_H. Reading from location 00000000_H reads from the input port. Writing to 00000000_H writes to the output port.

If the microprocessor writes a number to location 00000000_H and then reads location 00000000_H back it will not necessarily get the same number!

Suitable hardware for memory mapped I/O