memory rev 13072010
TRANSCRIPT
8/6/2019 Memory Rev 13072010
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B ASIC MICROPROCESSOR ²
SOFTWARE ARCHITECTUREThe Memory
8/6/2019 Memory Rev 13072010
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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
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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