2)linear select memory organization
- 1. LINEAR SELECT MEMORY ORGANIZATION PRESENTED BY GHOLAMREZA KAKAMANSHADI PANJAB UNIVERSITY, CHD, INDIA Aug,2014
- 2. • In any memory there must be a basic memory cell. • A basic memory cell is consist of an RS Flip-Flop with associated control circuitry. • The binary cell has three line inputs and one output. • The select input enables the cell for reading or writing and the read/write input determines the cell operation when it is selected.
- 4. Basic memory cell S Q Flip Flop R Q Select Input Write Output
- 5. Basic memory cell will be drawn as S I o W Note: To use this cell in a memory Technique Select cells by Memory address register Method to control selected cells written into or read from
- 6. S R State of flip-flop after clock ( Q ) 0 0 Unchanged 0 1 0 1 0 1 1 1 Not used S R Q 0 1 0 1 0 1 Q=S R S FLIP FLOP
- 7. Basic memory cell S Q R Q Select Input Write Output If Write =1 & Select = 1 Write Input into Q 1 1 1 1 1 0 1 0 1
- 8. Basic memory cell S Q R Q Select Input Write Output If Write =0 & Select=1 S=R=0 OUT= Q We read from 0 0 1 1 0 1 0 0 1 1 1 1
- 9. S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W 00 01 10 11 s R s R decoder Data Input MAR1 MAR2 Two flip-flop in MAR I1 I2 I3 Fig. A basic memory organization for Linear select IC memory Read Write Data OutputO1 O2 O3
- 10. Four address memory with 3 bits per word. The MAR selects the memory cells (Flip-Flop) to be read from or written into through a decoder which selects three Flip-Flop for each address that can be in the memory address register.
- 11. S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W 00 01 10 11 s R s R decoder MAR1 MAR2 Data Output I1 I2 I3 O1 O2 O3 Read Write Bit 1 Bit 2 Bit 3 Word 1 Word 2 Word 3 Word 4
- 12. There are four words and each row of three memory cells comprises a word. At any given time the MAR selects a word in memory. If the READ line is a 1 , the contents of the three cells in the selected word are READ out on the O1, O2,O3 lines. If the write line is a 1, the value on I1, I2, I3, are read into the memory.
- 13. Example : • If the second row in the memory contains 110 in the three memory cells and if MAR contains 01 , then the second out put line from the decoder will be 1, and the input gates and output gates to these three memory cells will be selected.
- 14. • If the READ line is a 1, then the outputs from the three memory cells in the second row will be 110 to the AND gates at bottom of the fig. So output of the memory will be 110
- 15. S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W 00 01 10 11 s R s R decoder MAR1 MAR2 Data Output I1 I2 I3 O1 O2 O3 Read Write 1 1 0 01 0 1 1 1 1 1 0
- 16. • If the write line is a 1 and the MAR again contains 01, the second row of flip-flops will have selected input. Then the input value on I1,I2,I3, will be read into the flip-flops in the second row.
- 17. S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W S I o W 00 01 10 11 s R s R decoder MAR1 MAR2 Data Output I1 I2 I3 O1 O2 O3 Read Write 1 0 1 01 0 1 1 1 1 0 1
- 18. There is only one problem with the memory: its complexity The basic memory cell is complicated, and for large memories the decoder will be large.
- 19. The End