Memory types

1. Memory Types
Session 3
SURYAPRAKASH S
suryaprakash.vsm@gmail.com
The resource for the PPT is made from variety of Books and online
PPT that were available in Internet. The Purpose of the PPT is made
for the Classroom Teaching.

2. Agenda
• Memory Types
• Memory Maps and Address
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3. Memory in
the System
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4. ROM, its uses and its
variants
• Non volatility
• Useful for embedded codes and data in
the system
• Mostly termed as Masked ROM, PROM,
OTP ROM, EPROM, and EEPROM
1. Masked ROM
2. EPROM, EEPROM, and OTP ROM
3. Used of ROM or EEPROM or Flash
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5. Masked ROM
• It is built from the circuit that has r input and 8
output i.e., Combinational Circuit
• Certain link fuse and others do not fuse
• The program will be provided to the manufacturing
foundry. (Locator).
• Manufacturing of 1000 pieces of ROM will be cost
effective
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6. EPROM, EEPROM and OTPROM
• EPROM-It is an ultraviolet ray erasable and device programmer PROM.
Erasing the device means restoring 1 at each bit in the cell array at each
ROM address.
• EEPROM erasing during an application –program run is done by sending all
eight data bus bits as 1s for the write in the presence if input of Vpp,
programming voltage for short write pulse.
• Flash Memory: is a form of EEPROM in which a sector of bytes can be
erased in a flash (very short duration of single clock cycle). The advantage
over EEPROM is that the erasing of many bytes simultaneously saves time
in each erase cycle that precedes the write cycle. Disadvantages is that
once erased takes more time in writing it.
• PROM: (an OTP ROM is an another form). Once written is not erasable.
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7. Uses if ROM or EEPROM or Flash
• EEPROM is usable by erasing over one million times. It can be erased
during runtime itself.
• Flash memory is usable about 10,000 times for repeated erasing
followed by programming during runtime.
• PROM is writer once by a device programmer or the first system run.
• Three examples of EEPROM memory
• Storing current date and time in a machine
• Storing port statuses.
• Storing driving , malfunctions and failure history in an automobile for use by
mechanics later on.
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8. RAM
• Various forms are SRAM, DRAM, NVRAM, ERORAM, SDRAM, RDRAM,
Parameterized Distributed RAM and Parameterized Block RAM.
• SRAM is used most commonly for designing caches and in embedded
system and microcontrollers.
• DRAM is used mostly in high performance computers or high memory
density system.
• EDO RAM is used in systems with buses to the device when operating with
clock rate up to 100 MHz.
• SDRAM synchronizes the read operation and keep the next word ready
while the precious one is being fetched.
• RDRAM accesses in burst the four successive words in a single fetch and
thus gives above 1GHz performance of the system.
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9. • Parameterized distributed RAM is the RAM distributes in various
system subunits. IO buffers and transceiver subunits can have a slice
of RAM each and the system stack can be at another slice.
Distribution provides buffering of memory at the subunits before they
are fetched and processed by the processor. It facilitates faster inputs
from the IO devices than the processor system buses access the IOs
using system memory.
• Parameterized block RAM is used when a specific block of the RAM is
dedicated for use by a subunits only, for example, MAC unit. A
parameterized block RAM is used when an access by the system or IO
or internal bus is slow compared to the processing speed of a subunit.
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