memory rev 13072010

8/6/2019 Memory Rev 13072010

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B ASIC MICROPROCESSOR ²

SOFTWARE ARCHITECTUREThe Memory

8/6/2019 Memory Rev 13072010



THE MEMORY

Memory is used to store program, data and

instruction, as patterns of 1s and 0s in a

temporary or permanent form.

Divided into two groups:1. ROM

2. RAM

8/6/2019 Memory Rev 13072010



ROM (READ ONLY MEMORY )

Nonvolatile memory because the stored data is

not lost when power to IC is turned off.

It contains the essential instruction for the

computer to start.

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ROM CONT.

Block Diagram Of

ROM

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ROM CONT.

Version of ROM:

1. Standard ROM

2. PROM

3. EPROM

4. EAROM

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1. STANDARD ROM

Data is fixed and not erasable, uses for fixed

program such as monitor for a system.

Called mask-programmable ROM.

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2. PROM (PROGRAMMABLE ROM)

Can be programmed by using electrically bit

pattern

Once it programmed the content cannot be

changed A memory element with un-blown fuse stores a ¶1·

and a blown fuse store ¶0·

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3. EPROM (ERASEABLE PROM)

Can be programmed, erased and then

programmed by the user as often as required

The information can be erased by flooding the

chip with ultra-violet Following this process the complete memory has

been erased, and new bit pattern can be entered

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4. EAROM (ELECTRICALLLY ALTERABLE

ROM)

Can be erased and programmable by a user.

The content of the complete memory can be

erased by applying voltage to appropriate pins of

the IC

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ROM AD V ANTAGES

1. Nonvolatile, and so they do not lose their

contents when power is lost

2. Cheaper than RAMs

3. More reliable than RAMs because theircircuitry is simpler

4. Static and do not require refresh

5. Easier to interface than RAMs

6. Cannot be accidently changed

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R AM (RANDOM ACCESS READ/WRITE

MEMORY )

Used for temporary storage or user programs and

data

Volatile memory because the stored data is lost

when the power supply to memory is switchedoff.

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R AM CONT.

Block Diagram Of RAM

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RAM CONT.

Divided in two groups:

1. SRAM

2. DRAM

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1. SRAM (STATIC RAM)

Contains flip-flop-like circuit as memory cells

Needs no refreshing and will holds its binary

information as long as the IC power is powered

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2. DRAM (DYNAMIC RAM)

Contains memory cell based on capacitance, the

cells must be refreshed hundreds of times per

second

Have advantage of higher capacity and lowerpower consumption over RAM

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DRAM CONT

DRAM types:

A. FPM

B. RDRAM

C. EDO

D. SDRAM

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I. FPM (FAST PAGE MODE)

Slightly faster than conventional DRAM.

While standard DRAM requires that a row and

column be sent for each access, FPM works by

sending the row address just once for manyaccesses to memory in locations near each other,

improving access time.

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II. RDRAM (RAMBUS DRAM)

Data is transferred on both the rising and falling

edges of the clock signal, a technique known as

double data rate

Slight increase in latency, heat output,manufacturing complexity, and cost

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III. EDO (EXTENDED DATA OUTPUT)

Faster than conventional DRAM

Unlike conventional DRAM which can only

access one block of data at a time, EDO RAM can

start fetching the next block of memory at thesame time that it sends the previous block to the

CPU

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I V. SDRAM (SYNCHRONOUS DRAM)

Synchronized with the system bus

Synchronous interface, meaning that it waits for

a clock signal before responding to control inputs

Enabling higher speeds

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R AM AD V ANTAGES

1. Simple to erase and reprogram

2. Can use for reprogramming purpose

3. Programming can be done quickly

4. Does not require programmer (equipment) toprogram

memory rev 13072010

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