Transcript Static Memory - Electrical and Computer Engineering

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 to 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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Static RAM Characteristics
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Forms the bulk of memory in a system.
Is read/write memory.
For read/write memory have choice of
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Special Characteristic Memory
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Static RAM
Dynamic RAM
ROM (PROM, EPROM, EEPROM)
EEPROM partially used as RAM
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
Wordwide 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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