Transcript Static Memory 9/20/6 Lecture 14 - Static Memory Static Memory 9/20/6 Lecture 14 - Static Memory.

Static Memory
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Lecture 14 - Static Memory
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Static Memory
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Static Memory Systems
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Those semiconductor components in a
microcomputer that store the program and
data.
Role in the system can be seen as passive –
memory simply stores information and except
for specialized architectures, performs no
operation on the data stored there.
Today it is common to have yyG bytes in a
system.
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RAM Characteristics
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Forms the bulk of memory in a system.
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Today the bulk memory is typically a flavor of DRAM
Is read/write memory.
For read/write memory have choice of
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Static RAM
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Dynamic RAM
Special Characteristic Memory
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ROM (PROM, EPROM, EEPROM)
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EEPROM partially used as RAM
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Computational Memory
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Static RAM
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Nonvolatile – as long as power is on value is retained
with no other action.
NMOS Memory cell
CMOS Memory cell
Select
Data
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Select
Vcc
Vcc
GND
GND
Data*
Data
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Data*
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Gate Equivalent
CMOS Memory cell
Select
Vcc
GND
Data*
Data
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st
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approach to 16K of RAM
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nd
2
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approach to 16K of RAM
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Internals of 6264LP Static CMOS
RAM
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A RAM Chip
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6264LP-10
-10 means
100ns access
time
Consider all
parameters
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Bus Contention
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Read after read to same chip
Must consider what happens in preceding
cycle and what happens in next cycle
Must also consider read after write, write after
read, and write after write timing
Timing for the same chip and for different
chips
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Read cycle bus contention
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Write cycle bus contention
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PROM and EPROM
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Programmable Read Only Memory
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Electrically Programmable Read Only
Memory
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One time programmable
Programmed by provided a higher than normal
programming voltage – 12V to 25V
UV erasable
Used to program and code startup code – the
bios in a PC
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PROM and EPROMS
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Come in many sizes
Byte wide is very common
Worldwide is also common
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EEPROM
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Another form of non-volatile memory
Read cycle is like other PROMs
Write cycle timing is long – typically over
100 us.
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EEPROMs and flash EEPROMs
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Flash EEPROMs are similar to electrical
erasable PROMs
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Example of flash EEPROM use
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Flash
EEPROMs
are similar
to
electrically
erasable
PROMs
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Wikipedia provides some info
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Wikipedia provides some useful overview of
the topic of the various non-volatile
technologies.
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