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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 Read and Write Operations

In the Reading data from memory and Writing data to memory sections, we considered the process of loading and storing data from the perspective of the microprocessor and in terms of signals on control wires and the buses. Now we look at what is involved from the perspective of the Random Access Memory (RAM) chips. At any given time, such RAM chips will be storing the active chunks of programs and associated data of the operating systems, browsers, word processors, compilers, etc. that we may be running on our computer. Computers with more and faster to access RAM generally outperform computers with less or slower RAM as their processors can manipulate more code and data faster without having to swap between memory and the hard drive.

Memory chips (and RAM in particular) have address wires, data wires, the read/write (R / W) wire, and the chip select (CS) wire.

When CS is high, the memory chip does nothing.

When CS is low and R / W is low, the memory chip writes the data on the data bus into the location indicated by the address bus. This allows the microprocessor to store data into memory.

When CS is low and R / W is high, the memory chip drives the data bus with the data from the location indicated by the address bus. This allows the microprocessor to load data out of memory into registers.