1. Memory Basics
Chapter 7

2. 7-1 Memory definitions
Memory is a collection of cells capable of storing binary information.
Two types of memory:
Random-Access Memory (RAM)
Read-Only Memory (ROM)

3. 7-2 Random-Access Memory
Memory cell can be accessed to transfer information to or from any desired location
Access will take the same time regardless of the location
compare to serial memory such as hard drive, tape etc.

4. Block diagram of memory

5. Example of memory content

6. Write and Read Operation
Apply the address on address lines (bus)
Apply data on data lines (bus)
Activate the Write input
Read
Activate the Read input

7. Timing waveforms
Operation of memory is controlled by an external device, such as CPU
Memory doesn’t employ CPU clock
Operations are timed by changes in values on control input
Access time for read: max. time from application of address to appearance of data on Data Output
Write cycle time: max. time form application of address to completion of all operation required to store a word

8. Timing waveforms
4 clocks is needed for both Write cycle and Access time

9. Properties of memory
Volatile: data disappeared after turning off the power
Static RAM (SRAM): faster, less capacity
Dynamic RAM (DRAM): slower, need refresh, more capacity
Non-volatile: date kept after turning off the power
Magnetic disk

10. 7-3 SRAM Integrated Circuits
Static RAM cell

11. RAM bit slice model

12. 16-word by one-bit RAM chip

13. Coincident selection (16x1 RAM using 4x4 cell array)

14. Coincident selection (8x2 RAM using 4x4 cell array)

15. 7-4 Array of SRAM ICs
Symbol for 64K x 8 RAM

16. Block diagram of a 256K x 8 RAM
Extension from 64K x 8 RAM
Fig. 8-10

17. Block diagram of a 64K x 16 RAM