Microprocessor and Computer Architecture

  1. Home
  2. Docs
  3. Microprocessor and Comput...
  4. Memory Organization
  5. Main Memory

Main Memory

Characteristics of Main Memory

‣ Volatility:

‣ Speed:

‣ Size:

‣ Addressability:

Functions of Main Memory

‣ Program Execution:

‣ Data Storage:

‣ Operating System Usage:

‣ Temporary Storage:

Types of Main Memory
  • Requires constant refreshing to maintain the integrity of stored data.
  • Less expensive compared to SRAM (Static RAM).
  • Higher density, allowing for larger storage capacities.
  • Slower compared to SRAM.
  • A RAM chip is better suited for communication with the CPU if it has one or more control inputs that select the chip only when needed.
  • Another common features is a bidirectional data bus that allows the transfer of data either from memory to CPU during a read operation , or from CPU to memory during a write operation.
  • A bidirectional bus can be constructed with three state buffer: a signal equivalent to logic 1 , a signal equivalent to logic 0, or a high – impedance state.
  • The logic 1 and 0 are normal digital signals.
  • The high impedance state behaves like an open circuit, which means that the output doesn’t carry a signal and has no logic significance.
Screenshot 2024 03 31 171911
Screenshot 2024 03 31 173429

Memory Address Map is a pictorial representation of assigned address space for
each chip in the system.

  • To demonstrate an example, assume that a computer system needs 512 bytes of RAM and 512 bytes of ROM
  • The RAM have 128 byte and need seven address lines, where the ROM have 512
    bytes and need 9 address lines.
Screenshot 2024 03 31 173940

The hexadecimal address assigns a range of hexadecimal equivalent address
for each chip.

  • Line 8 and 9 represent four distinct binary combination to specify which RAM we chose
  • When line 10 is 0, CPU selects a RAM. And when it’s 1, it selects the ROM.
Screenshot 2024 03 31 174214

How can we help?

Leave a Reply

Your email address will not be published. Required fields are marked *