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Memory BasicsChapter 8

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RAM Random access memory

ROM Read-only memory

Memory definitions

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RAM

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Control inputs to a memory chip

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Static RAM (SRAM) Consists of internal latches that store the

binary information Dynamic RAM (DRAM)

Stores the binary information in the form of electric charges on capacitors

Properties of memory

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若 Bit select為 1，則接通 1, 2 gates。為1，寫入資料， 3, 4接通。Data in之後產生 B, ，再選word，選到的 5,6,7,8接通，此時不是 Set就是Reset，傳入C或。在Read logic S, R其一為 1，經 2輸出。

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16-word by 1-bit RAM chip

IN

EN

OUT

Three-state buffer

EN IN OUT

0 X Hi-Z

1 0 0

1 1 1

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16x1 RAM using a4x4 RAM cell array

Reduce number of1. Decoder gates2. Inputs per gate3. RAM cells per slice

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8x2 RAM using a4x4 RAM cell array

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A 32K x 8 RAM 32K x 8=215*23=218

Each column 29

Example

9-29

decoder

6-26

decoder

215

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64K x 8 RAM

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256K x 8 RAM

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64K x 16 RAM