1. Chapter 8 Memory Basics ( 메모리 기초 ) 8-1 Memory 의 정의 8-2 RAM 8-3 SRAM IC ( 집적회로 ) 8-4 SRAM IC 의 배열 8-5 DRAM IC 8-6 DRAM 유형 8-7 SRAM IC 의 배열

2. 8-1 Definition  RAM (Random Access Memory) ; Accepts new info. for storage to be available later for use. ; Read : The process of transferring the stored info. out of memory. Write : The process of storing new info. in memory.  ROM (Read Only memory) ; Programmable logic device 의 한 종류 ; 이러한 device 에 저장되는 binary info. 는 어떤 특정한 형태로 표시되어진 후에 computer 내부의 H/W 에 embedded 된다. → 이러한 과정을 device 를 programming 한다 라고 한다. ; Programming refers to a H/W procedure that specifies the bits that are inserted into the H/W configuration of the device ; Only Read operation is possible.

3. 8-2 Random Access Memory  Memory cell can be accessed to transfer information to and from any location, with the access taking the same time regardless of the location.  Word ; An entity of bits that moves in and out of memory. ; A group of 1's and 0's represents a number, an instruction, alphanumeric characters, etc... ; 8 bits = 1 byte, ; 16-bit word, 32-bit word,... multiple of 8bits (1 byte)

4. Memory Block Diagram  Address lines select one particular word. Each word in memory is assigned an identical number called an "address". ; k address lines means that addresses range from 0 ∼ 2 k -1. ; (1K ×16), (64K ×10) memory [ 그림 8-1] 메모리 블럭 다이어그램

5. (1024 X 16) Memory 의 내용  16 bit 크기의 워드로 된 1K Word Memory 1K = 2 10, 16-bit = 2 Byte, 따라서 2048 즉 2K Byte Memory 임 [ 그림 8-2] 1024 ⅹ 16 메모리의 저장 내용

6.  Memory write 1. Apply the binary address of the desired word to the address lines. 2. Apply the data bits that must be stored in memory to the data input lines. 3. Activate the Write input.  Memory read 1. Apply the binary address of the desired word to the address lines. 2. Activate the Read input.  Memory is made up of RAM IC(chips), plus additional logic circuits.  Read/bar Write control line 사용. Write and Read Operations Chip Select Read/Write Memory CS R/W Operation 0 X None 1 0 Write to selected word 1 X Read from selected word

7. Memory Write Cycle Timing Waveform (Fig.8-3) Write Cycle  Write cycle time ; Maximum time from the application of the address to the completion of all internal memory operations required to store a word.  The access time and the write cycle time of the memory must be related within the CPU to a period equal to a fixed number of CPU clock pulse period.  Write cycle time : 75 ㎱, 4 clock pulses

8. Memory Read Cycle Timing Waveform (Fig.8-3) Read Cycle  Access time of memory read operation ; Maximum time from the application of the address to the appearance of the data at Data Output  The access time and the write cycle time of the memory must be related within the CPU to a period equal to a fixed number of CPU clock pulse period.  Read cycle : 65 ㎱, needs 4 clock pulses

9. Properties of Memory  Static RAM (SRAM) ; The stored info. remains valid as long as power is applied.  Dynamic RAM (DRAM) ; Stores binary info.in the form of electric charges on capacitors. ; The capacitors must be periodically recharged by refreshing. This is done by cycling through the words every few ㎳, reading and rewriting them to restore the decaying the charge. ; Offers reduced power consumption.  Volatile memory : RAMs  Non volatile memory : ROM, Magnetic memory, etc.