Chapter 16 Semiconductor, Magnetic and Optical Memory 1.

Chapter 16Chapter 16

Semiconductor, Magnetic and Semiconductor, Magnetic and Optical MemoryOptical Memory

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ObjectivesObjectives

You should be able to:You should be able to: Explain the basic concepts involved in Explain the basic concepts involved in

memory addressing and data storage.memory addressing and data storage. Interpret the specific timing Interpret the specific timing

requirements given in a manufacturer’s requirements given in a manufacturer’s data manual for reading ro writing to a data manual for reading ro writing to a memory IC.memory IC.

Discuss the operation and application Discuss the operation and application for the various types of semiconductor for the various types of semiconductor memory ICs.memory ICs.

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ObjectivesObjectives

(Continued)(Continued) Design circuitry to facilitate memory Design circuitry to facilitate memory

expansion.expansion. Explain the refresh procedure for Explain the refresh procedure for

dynamic RAMs.dynamic RAMs. Explain the differences between the Explain the differences between the

various types of magnetic and optical various types of magnetic and optical storage.storage.

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Memory ConceptsMemory Concepts

Memory locations Memory locations have memory have memory addressesaddresses

Data are the Data are the memory contentsmemory contents

8 bits known as a 8 bits known as a bytebyte

Example layout for Example layout for sixteen 8-bit sixteen 8-bit memory locationsmemory locations

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Logic Logic Diagram for Diagram for a circuit to a circuit to implement a implement a 16-bit 16-bit memorymemory

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Figure 16-3: A typical timing Figure 16-3: A typical timing diagram a manufacturer might use diagram a manufacturer might use to show timing parameters for a bus to show timing parameters for a bus driven devicedriven device Data and address lines are grouped Data and address lines are grouped

together with an X to show where they together with an X to show where they are allowed to change or crossoverare allowed to change or crossover

Setup time Setup time ttss Propagation delay Propagation delay ttpp

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Memory Concepts Memory Concepts (Figure 16-3)(Figure 16-3)

Static RAMsStatic RAMs

Random-Access MemoryRandom-Access Memory Read/Write MemoryRead/Write Memory Temporary storage of data (volatile)Temporary storage of data (volatile) User can access data at any location User can access data at any location

randomlyrandomly CD player or Hard DiskCD player or Hard Disk Static or DynamicStatic or Dynamic

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StaticStatic Flip-flops as basic storage elementsFlip-flops as basic storage elements

DynamicDynamic Capacitors as basic storage elementsCapacitors as basic storage elements Requires additional refresh circuitryRequires additional refresh circuitry Can be densely packedCan be densely packed Low cost per bitLow cost per bit

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The 2147H Static MOS RAMThe 2147H Static MOS RAM 4096 memory locations4096 memory locations

4k = 4 x 1024 = 40964k = 4 x 1024 = 4096 Each location can contain 1 bitEach location can contain 1 bit 4096 unique addresses needs 24096 unique addresses needs 21212 = =

4096 address lines4096 address lines AA00 to A to A55 identify rows identify rows

AA66 to A to A1111 identify columns identify columns

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2147H Static MOS RAM2147H Static MOS RAM

Read cycle Read cycle waveformswaveforms

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2147 H Static MOS 2147 H Static MOS RAMRAM

Write cycle Write cycle waveformswaveforms

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Memory Expansion: Using multiple Memory Expansion: Using multiple chips to get more memory capacitychips to get more memory capacity Eight 4K chipsEight 4K chips

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Dynamic RAMsDynamic RAMs

Require more support circuitryRequire more support circuitry More difficult to useMore difficult to use Less expensive per bitLess expensive per bit Higher density, smaller size per bitHigher density, smaller size per bit Charge is placed on capacitor in Charge is placed on capacitor in

each memory locationeach memory location

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Simplified DRAM read and write Simplified DRAM read and write operationoperation

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Usually multiplex address linesUsually multiplex address lines Capacitor refreshed during Capacitor refreshed during

refresh cyclerefresh cycle

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Refresh cycle timingRefresh cycle timing Usually every 2 ms or lessUsually every 2 ms or less Three ways to refresh memory cells:Three ways to refresh memory cells:

Read cycleRead cycle Write cycleWrite cycle RAS-only cycleRAS-only cycle

RAS only proceduresRAS only procedures1.1. CAS is HIGHCAS is HIGH

2.2. AA00 to A to A66 are set up with row address 000 0000 are set up with row address 000 0000

3.3. RAS is pulsed LOWRAS is pulsed LOW

4.4. Increment the AIncrement the A00 to A to A66 row address by 1 row address by 1

5.5. Repeat 3 and 4 until all 128 rows accessedRepeat 3 and 4 until all 128 rows accessed

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Dynamic RAM Dynamic RAM ControllersControllers Simplify Simplify

demultiplexing demultiplexing and refreshingand refreshing

Intel 3242 Intel 3242

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Read-Only MemoriesRead-Only Memories

Store data on a permanent basisStore data on a permanent basis NonvolatileNonvolatile EPROMEPROM

Erasable-programmable-read-only Erasable-programmable-read-only memorymemory

Useful for storage of:Useful for storage of: Operating systemsOperating systems Table look-upsTable look-ups Language compilersLanguage compilers

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Mask ROMsMask ROMs One-time fee to design a unique maskOne-time fee to design a unique mask Very inexpensive after one-time feeVery inexpensive after one-time fee

Fusible-Link PROMsFusible-Link PROMs Avoid one-time feeAvoid one-time fee Every memory cell has a fusible linkEvery memory cell has a fusible link Burned open to permanently store dataBurned open to permanently store data

PROM programmer or MDS PROM programmer or MDS (microprocessor development system)(microprocessor development system)

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EPROMsEPROMs Can change the memory contentsCan change the memory contents Expose an open window to ultraviolet light to Expose an open window to ultraviolet light to

eraseerase Slowest erasure timeSlowest erasure time

EEPROMsEEPROMs Non-volatileNon-volatile Erased while in circuitErased while in circuit Individual bits erasedIndividual bits erased

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Flash MemoryFlash Memory Faster access timesFaster access times Erase entire blocks quicklyErase entire blocks quickly Digital cameras and PDAsDigital cameras and PDAs

Floating-gate MOSFET usedFloating-gate MOSFET used Charge remains on gate for 10 yearsCharge remains on gate for 10 years

-OTP (one-time-programming)-OTP (one-time-programming) Timing requirements must be metTiming requirements must be met

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Read-Only MemoriesRead-Only Memories 2716 EPROM read cycle2716 EPROM read cycle

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2716 EPROM program cycle2716 EPROM program cycle

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Memory Expansion and Memory Expansion and Address Decoding Address Decoding

ApplicationsApplications Address Address

DecodingDecoding To identify To identify

which IC is to which IC is to be read or be read or written towritten to

Address Address decoding decoding scheme 16k-scheme 16k-byte EPROM byte EPROM (4 x 4k)(4 x 4k) 27

Memory Expansion and Memory Expansion and Address Decoding Address Decoding

ApplicationsApplications A PROM Look-Up TableA PROM Look-Up Table

See Application 16-1See Application 16-1 A Digital LCD ThermometerA Digital LCD Thermometer

See Application 16-2See Application 16-2

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Application 16-1 Application 16-1 Prom Lookup TableProm Lookup Table

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Application 2Application 2Digital LCD Digital LCD

ThermometerThermometer

Magnetic and Optical Magnetic and Optical StorageStorage

Electro-mechanical in natureElectro-mechanical in nature Non-volatileNon-volatile MagneticMagnetic

North-south or south-north polaritiesNorth-south or south-north polarities OpticalOptical

Pits and lands read by a laser systemPits and lands read by a laser system Slower and bulkier but less Slower and bulkier but less

expensive with higher storage expensive with higher storage capacitiescapacities

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Magnetic memory; The floppy Magnetic memory; The floppy disk and hard diskdisk and hard disk Magnetizable mediumMagnetizable medium Rigid plastic jacketRigid plastic jacket FloppyFloppy

300 rpm300 rpm Two read/write heads (one each side)Two read/write heads (one each side) 1.44 MB1.44 MB RemovableRemovable Transfer rates of 45KB/secTransfer rates of 45KB/sec

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Magnetic memory; The floppy Magnetic memory; The floppy disk and hard diskdisk and hard disk Hard diskHard disk

Not removableNot removable Rigid plattersRigid platters Sealed unitSealed unit Multiple two-sided plattersMultiple two-sided platters One read/write head for each platter One read/write head for each platter

surfacesurface Thousands of rpmsThousands of rpms Gigabytes of storage capacityGigabytes of storage capacity

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Magnetic memory; The floppy disk Magnetic memory; The floppy disk and hard diskand hard disk Hard diskHard disk

Controlled internal environmentControlled internal environment Bits closely packedBits closely packed Concentric circles called tracks (cylinders)Concentric circles called tracks (cylinders) 20,000 tracks per inch20,000 tracks per inch 300K bits per inch on each track300K bits per inch on each track Transfer rates of 30 MB/secTransfer rates of 30 MB/sec

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Magnetic memory; The floppy disk Magnetic memory; The floppy disk and hard diskand hard disk Removable hard disksRemovable hard disks

Zip diskZip disk 300 rpm300 rpm 100 MB100 MB

Jaz cartridgeJaz cartridge Two rigid plattersTwo rigid platters 2 GB2 GB

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Optical memoryOptical memory CDCD

Not as fast as hard disksNot as fast as hard disks RemovableRemovable 650 MB650 MB Aluminum alloy coatingAluminum alloy coating Rigid polycarbonate waferRigid polycarbonate wafer Pits = 1 Lands = 0Pits = 1 Lands = 0

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Optical memoryOptical memory CDCD

One track starting at center and spiraling One track starting at center and spiraling outwardoutward

16,000 tracks per inch16,000 tracks per inch Thin plastic coating to protectThin plastic coating to protect Land reflects light, pit does notLand reflects light, pit does not

CD-RCD-R Photosensitive dye on reflective gold layerPhotosensitive dye on reflective gold layer Laser super heats spot and it will not reflectLaser super heats spot and it will not reflect Cannot be erased or re-writtenCannot be erased or re-written

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Optical memoryOptical memory CD-RWCD-RW

Silver alloy crystalline structureSilver alloy crystalline structure Laser superheats to amorphous state (non-Laser superheats to amorphous state (non-

reflective)reflective) Laser can reheat at lower level to turn back Laser can reheat at lower level to turn back

into crystalline stateinto crystalline state Reflective and non-reflective areasReflective and non-reflective areas

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SummarySummary

A simple 16-byte memory circuit can A simple 16-byte memory circuit can be constructed from 16 octal D flip-be constructed from 16 octal D flip-flops and a decoder. This circuit flops and a decoder. This circuit would have 16 memory locations would have 16 memory locations (addresses) selectable by the (addresses) selectable by the decoder, with 1 byte (8 bits) of data decoder, with 1 byte (8 bits) of data at each location.at each location.

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SummarySummary

Static RAM (random-access memory) Static RAM (random-access memory) ICs are also called read/write ICs are also called read/write memory. They are used for the memory. They are used for the temporary storage of data and temporary storage of data and program instructions in program instructions in microprocessor-based systems.microprocessor-based systems.

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SummarySummary

A typical RAM IC is the 2114A. It is A typical RAM IC is the 2114A. It is organized as 1k organized as 1k 4, which means 4, which means that it has 1k locations, with 4 bits of that it has 1k locations, with 4 bits of data at each location. (1k is actually data at each location. (1k is actually represents 2represents 21010 = 1024.) An example = 1024.) An example of a higher-density RAM IC is the of a higher-density RAM IC is the 6206, which is organized as 32k 6206, which is organized as 32k 8. 8.

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SummarySummary

Dynamic RAMs are less expensive Dynamic RAMs are less expensive per bit and have a much higher per bit and have a much higher density than static RAMs. Their density than static RAMs. Their basic storage element is an internal basic storage element is an internal capacitor at each memory cell. capacitor at each memory cell. External circuitry is required to External circuitry is required to refresh the charge on all capacitors refresh the charge on all capacitors every 2 ms or less.every 2 ms or less.

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SummarySummary

Dynamic RAMs generally multiplex Dynamic RAMs generally multiplex their address bus. This mean that their address bus. This mean that the high-order address bits share the the high-order address bits share the same pins as the low-order address same pins as the low-order address bits. They are demultiplexed by the bits. They are demultiplexed by the RAS and CAS (Row Address Strobe RAS and CAS (Row Address Strobe and Column Address Strobe) control and Column Address Strobe) control signals.signals.

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SummarySummary

Read-only memory (ROM) is used to Read-only memory (ROM) is used to store data on a permanent basis. It store data on a permanent basis. It is nonvolatile, which means that it is nonvolatile, which means that it does not lose its memory contents does not lose its memory contents when power is removed.when power is removed.

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SummarySummary

Three common ROMs are (1) the Three common ROMs are (1) the mask ROM, which is programmed mask ROM, which is programmed once by a masking process by the once by a masking process by the manufacturer; (2) the fusible-link manufacturer; (2) the fusible-link programmable ROM (PROM), which programmable ROM (PROM), which is programmed once by the user; and is programmed once by the user; and (3) the erasable-programmable ROM (3) the erasable-programmable ROM (EPROM), which is programmable (EPROM), which is programmable and UV-erasable by the user.and UV-erasable by the user.

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SummarySummary Memory expansion in microprocessor Memory expansion in microprocessor

systems is accomplished by using octal systems is accomplished by using octal or hexadecimal decoders as address or hexadecimal decoders as address decoders to select the appropriate decoders to select the appropriate memory IC.memory IC.

The Electrically-Erasable PROM The Electrically-Erasable PROM (EEPROM) and Flash memory use a (EEPROM) and Flash memory use a floating-gate MOSFET for their floating-gate MOSFET for their primary storage element. A charge on primary storage element. A charge on the floating gate represents the stored the floating gate represents the stored data.data.

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SummarySummary

Magnetic storage like the floppy or Magnetic storage like the floppy or hard disk use magnetized particles to hard disk use magnetized particles to represent the stored 1 or 0. Individual represent the stored 1 or 0. Individual data bits are read and written using an data bits are read and written using an electro-magnetic read/write head.electro-magnetic read/write head.

Optical memory like the CD or DVD Optical memory like the CD or DVD use a laser beam to reflect light off of a use a laser beam to reflect light off of a rigid platter. The CD or DVD platter rigid platter. The CD or DVD platter will either have a non-reflective pit to will either have a non-reflective pit to represent a 1 or a non-pit (land) to represent a 1 or a non-pit (land) to represent a 0.represent a 0.

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Chapter 16 Semiconductor, Magnetic and Optical Memory 1.

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