Memory & Programmable Implementation Technologies

1. Electrical Engineering Department Third Year E/C Digital Electronic Circuits • Memory • & • Programmable Implementation Technologies CH-3 Prepared by: Diary R. Sulaiman 2018 Prepared by: Diary R. Sulaiman

2. Contents- Computer & Memory- Memory definition- Memory Capacity- Memory as a Digital storage- Memory Block Diagram- Basic Memory Operations- Memory hierarchy- memory Organization on Chip- Programmable Implementations Prepared by: Diary R. Sulaiman 2

3. Memory? • In digital systems Memoryis a device in which binary digits (“0” or “1”) are stored, and when again required are retrieved. • The stored process termed as writing. • The retrieving termed as reading. • The simplest example of single bit memory is a flip flop. • SET – “1” has been written in it. • RESET – “0” has been written in it. • The stored “written” bit can be read from its “Q” out. • 4-flip flops can provide memory capacity of 4-bits. Prepared by: Diary R. Sulaiman

4. Memory • Memory unit stores instructions and data. • Recall, data is represented as a series of bits. • To store data, memory unit thus stores bits. • Processor reads instructions and reads/writes data from/to the memory during the execution of a program. • In theory, instructions and data could be fetched one bit at a time. • In practice, a group of bits is fetched at a time(WORD). • In order to read/write to and from memory, a processor should know where to look: • “Address” is associated with each word location. Prepared by: Diary R. Sulaiman

5. Basic Memory Operations • Memory operations require the following: • Data─ data written to, or read from, memory as required by the operation. • Address─ specifies the memory location to operate on. The address lines carry this information into the memory. Typically: n bits specify locations of 2n words. • An operation or Control─ Information sent to the memory and interpreted as control information which specifies the type of operation to be performed. Typical operations are READ and WRITE. Prepared by: Diary R. Sulaiman

6. Basic Memory Operations (continued) • Instead of separate Read and Write control lines, most ICs provide a ChipSelect that selects the chip to be read from or written to and a Write/Readthat determines the particular operation. Prepared by: Diary R. Sulaiman

7. Memory speed • Access time (Ta) • - the average time taken to reada unit of information • e.g., 100 ns • Access rate (Ra) = 1/Ta (bits/second) • e.g., 1/100ns = 10 Mb/s • Cycle time (Tc) • - the average time lapse between two successive read operations • e.g., 500 ns • Bandwidth or transfer rate (Rc) = 1/Tc (bits/second) • e.g., 1/500ns = 2 Mb/s Prepared by: Diary R. Sulaiman

8. RAM Memory (DRAM) CPU Cache Memory (SRAM) = Bus connections The operation of cache memory 1. Cache fetches data from next to current addresses in main memory 2. CPU checks to see whether the next instruction it requires is in cache 3. If it is, then the instruction is fetched from the cache – a very fast position 4. If not, the CPU has to fetch next instruction from main memory - a much slower process Prepared by: Diary R. Sulaiman

9. Stating RAM Structure Prepared by: Diary R. Sulaiman

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11. Typical 16 Mb DRAM (4M x 4) Prepared by: Diary R. Sulaiman

12. Packaging Prepared by: Diary R. Sulaiman

13. 1MByte Module Organisation Prepared by: Diary R. Sulaiman