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Chapter 16 Semiconductor, Magnetic and Optical Memory 1.

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Presentation on theme: "Chapter 16 Semiconductor, Magnetic and Optical Memory 1."— Presentation transcript:

1 Chapter 16 Semiconductor, Magnetic and Optical Memory 1

2 Objectives You should be able to: Explain the basic concepts involved in memory addressing and data storage. Explain the basic concepts involved in memory addressing and data storage. Interpret the specific timing requirements given in a manufacturers data manual for reading ro writing to a memory IC. Interpret the specific timing requirements given in a manufacturers data manual for reading ro writing to a memory IC. Discuss the operation and application for the various types of semiconductor memory ICs. Discuss the operation and application for the various types of semiconductor memory ICs. 2

3 Objectives (Continued) Design circuitry to facilitate memory expansion. Design circuitry to facilitate memory expansion. Explain the refresh procedure for dynamic RAMs. Explain the refresh procedure for dynamic RAMs. Explain the differences between the various types of magnetic and optical storage. Explain the differences between the various types of magnetic and optical storage. 3

4 Memory Concepts Memory locations have memory addresses Memory locations have memory addresses Data are the memory contents Data are the memory contents 8 bits known as a byte 8 bits known as a byte Example layout for sixteen 8-bit memory locations Example layout for sixteen 8-bit memory locations 4

5 Memory Concepts Logic Diagram for a circuit to implement a 16- bit memory Logic Diagram for a circuit to implement a 16- bit memory 5

6 Memory Concepts Figure 16-3: A typical timing diagram a manufacturer might use to show timing parameters for a bus driven device Figure 16-3: A typical timing diagram a manufacturer might use to show timing parameters for a bus driven device Data and address lines are grouped together with an X to show where they are allowed to change or crossover Data and address lines are grouped together with an X to show where they are allowed to change or crossover Setup time t s Setup time t s Propagation delay t p Propagation delay t p 7

7 8 Memory Concepts (Figure 16-3)

8 Static RAMs Random-Access Memory Random-Access Memory Read/Write Memory Read/Write Memory Temporary storage of data (volatile) Temporary storage of data (volatile) User can access data at any location randomly User can access data at any location randomly CD player or Hard Disk CD player or Hard Disk Static or Dynamic Static or Dynamic 9

9 Static RAMs Static Static Flip-flops as basic storage elements Flip-flops as basic storage elements Dynamic Dynamic Capacitors as basic storage elements Capacitors as basic storage elements Requires additional refresh circuitry Requires additional refresh circuitry Can be densely packed Can be densely packed Low cost per bit Low cost per bit 10

10 Static RAMs The 2147H Static MOS RAM The 2147H Static MOS RAM 4096 memory locations 4096 memory locations 4k = 4 x 1024 = k = 4 x 1024 = 4096 Each location can contain 1 bit Each location can contain 1 bit 4096 unique addresses needs 2 12 = 4096 address lines 4096 unique addresses needs 2 12 = 4096 address lines A 0 to A 5 identify rows A 0 to A 5 identify rows A 6 to A 11 identify columns A 6 to A 11 identify columns 11

11 2147H Static MOS RAM Read cycle waveforms Read cycle waveforms 12

12 2147 H Static MOS RAM Write cycle waveforms Write cycle waveforms 13

13 Static RAMs Memory Expansion: Using multiple chips to get more memory capacity Memory Expansion: Using multiple chips to get more memory capacity Eight 4K chips Eight 4K chips 14

14 Dynamic RAMs Require more support circuitry Require more support circuitry More difficult to use More difficult to use Less expensive per bit Less expensive per bit Higher density, smaller size per bit Higher density, smaller size per bit Charge is placed on capacitor in each memory location Charge is placed on capacitor in each memory location 15

15 Dynamic RAMs Simplified DRAM read and write operation Simplified DRAM read and write operation 16

16 Dynamic RAMs Usually multiplex address lines Usually multiplex address lines Capacitor refreshed during refresh cycle Capacitor refreshed during refresh cycle 17

17 Dynamic RAMs Refresh cycle timing Refresh cycle timing Usually every 2 ms or less Usually every 2 ms or less Three ways to refresh memory cells: Three ways to refresh memory cells: Read cycle Read cycle Write cycle Write cycle RAS-only cycle RAS-only cycle RAS only procedures RAS only procedures 1. CAS is HIGH 2. A 0 to A 6 are set up with row address RAS is pulsed LOW 4. Increment the A 0 to A 6 row address by 1 5. Repeat 3 and 4 until all 128 rows accessed 18

18 Dynamic RAMs Dynamic RAM Controllers Dynamic RAM Controllers Simplify demultiplexing and refreshing Simplify demultiplexing and refreshing Intel 3242 Intel

19 Read-Only Memories Store data on a permanent basis Store data on a permanent basis Nonvolatile Nonvolatile EPROM EPROM Erasable-programmable-read-only memory Erasable-programmable-read-only memory Useful for storage of: Useful for storage of: Operating systems Operating systems Table look-ups Table look-ups Language compilers Language compilers 20

20 Read-Only Memories Mask ROMs Mask ROMs One-time fee to design a unique mask One-time fee to design a unique mask Very inexpensive after one-time fee Very inexpensive after one-time fee Fusible-Link PROMs Fusible-Link PROMs Avoid one-time fee Avoid one-time fee Every memory cell has a fusible link Every memory cell has a fusible link Burned open to permanently store data Burned open to permanently store data PROM programmer or MDS (microprocessor development system) PROM programmer or MDS (microprocessor development system) 21

21 Read-Only Memories EPROMs EPROMs Can change the memory contents Can change the memory contents Expose an open window to ultraviolet light to erase Expose an open window to ultraviolet light to erase Slowest erasure time Slowest erasure time EEPROMs EEPROMs Non-volatile Non-volatile Erased while in circuit Erased while in circuit Individual bits erased Individual bits erased 22

22 Read-Only Memories Flash Memory Flash Memory Faster access times Faster access times Erase entire blocks quickly Erase entire blocks quickly Digital cameras and PDAs Digital cameras and PDAs Floating-gate MOSFET used Floating-gate MOSFET used Charge remains on gate for 10 years Charge remains on gate for 10 years -OTP (one-time-programming) -OTP (one-time-programming) Timing requirements must be met Timing requirements must be met 23

23 Read-Only Memories 24

24 Read-Only Memories 2716 EPROM read cycle 2716 EPROM read cycle 25

25 Read-Only Memories 2716 EPROM program cycle 2716 EPROM program cycle 26

26 Memory Expansion and Address Decoding Applications Address Decoding Address Decoding To identify which IC is to be read or written to To identify which IC is to be read or written to Address decoding scheme 16k-byte EPROM (4 x 4k) Address decoding scheme 16k-byte EPROM (4 x 4k) 27

27 Memory Expansion and Address Decoding Applications A PROM Look-Up Table A PROM Look-Up Table See Application 16-1 See Application 16-1 A Digital LCD Thermometer A Digital LCD Thermometer See Application 16-2 See Application

28 29 Application 16-1 Prom Lookup Table

29 30

30 31 Application 2 Digital LCD Thermometer

31 Magnetic and Optical Storage Electro-mechanical in nature Electro-mechanical in nature Non-volatile Non-volatile Magnetic Magnetic North-south or south-north polarities North-south or south-north polarities Optical Optical Pits and lands read by a laser system Pits and lands read by a laser system Slower and bulkier but less expensive with higher storage capacities Slower and bulkier but less expensive with higher storage capacities 32

32 Magnetic and Optical Storage Magnetic memory; The floppy disk and hard disk Magnetic memory; The floppy disk and hard disk Magnetizable medium Magnetizable medium Rigid plastic jacket Rigid plastic jacket Floppy Floppy 300 rpm 300 rpm Two read/write heads (one each side) Two read/write heads (one each side) 1.44 MB 1.44 MB Removable Removable Transfer rates of 45KB/sec Transfer rates of 45KB/sec 33

33 Magnetic and Optical Storage Magnetic memory; The floppy disk and hard disk Magnetic memory; The floppy disk and hard disk Hard disk Hard disk Not removable Not removable Rigid platters Rigid platters Sealed unit Sealed unit Multiple two-sided platters Multiple two-sided platters One read/write head for each platter surface One read/write head for each platter surface Thousands of rpms Thousands of rpms Gigabytes of storage capacity Gigabytes of storage capacity 34

34 Magnetic and Optical Storage Magnetic memory; The floppy disk and hard disk Magnetic memory; The floppy disk and hard disk Hard disk Hard disk Controlled internal environment Controlled internal environment Bits closely packed Bits closely packed Concentric circles called tracks (cylinders) Concentric circles called tracks (cylinders) 20,000 tracks per inch 20,000 tracks per inch 300K bits per inch on each track 300K bits per inch on each track Transfer rates of 30 MB/sec Transfer rates of 30 MB/sec 35

35 Magnetic and Optical Storage Magnetic memory; The floppy disk and hard disk Magnetic memory; The floppy disk and hard disk Removable hard disks Removable hard disks Zip disk Zip disk 300 rpm 300 rpm 100 MB 100 MB Jaz cartridge Jaz cartridge Two rigid platters Two rigid platters 2 GB 2 GB 36

36 Magnetic and Optical Storage Optical memory Optical memory CD CD Not as fast as hard disks Not as fast as hard disks Removable Removable 650 MB 650 MB Aluminum alloy coating Aluminum alloy coating Rigid polycarbonate wafer Rigid polycarbonate wafer Pits = 1 Lands = 0 Pits = 1 Lands = 0 37

37 Magnetic and Optical Storage Optical memory Optical memory CD CD One track starting at center and spiraling outward One track starting at center and spiraling outward 16,000 tracks per inch 16,000 tracks per inch Thin plastic coating to protect Thin plastic coating to protect Land reflects light, pit does not Land reflects light, pit does not CD-R CD-R Photosensitive dye on reflective gold layer Photosensitive dye on reflective gold layer Laser super heats spot and it will not reflect Laser super heats spot and it will not reflect Cannot be erased or re-written Cannot be erased or re-written 38

38 Magnetic and Optical Storage Optical memory Optical memory CD-RW CD-RW Silver alloy crystalline structure Silver alloy crystalline structure Laser superheats to amorphous state (non-reflective) Laser superheats to amorphous state (non-reflective) Laser can reheat at lower level to turn back into crystalline state Laser can reheat at lower level to turn back into crystalline state Reflective and non-reflective areas Reflective and non-reflective areas 39

39 Summary A simple 16-byte memory circuit can be constructed from 16 octal D flip-flops and a decoder. This circuit would have 16 memory locations (addresses) selectable by the decoder, with 1 byte (8 bits) of data at each location. A simple 16-byte memory circuit can be constructed from 16 octal D flip-flops and a decoder. This circuit would have 16 memory locations (addresses) selectable by the decoder, with 1 byte (8 bits) of data at each location. 40

40 Summary Static RAM (random-access memory) ICs are also called read/write memory. They are used for the temporary storage of data and program instructions in microprocessor-based systems. Static RAM (random-access memory) ICs are also called read/write memory. They are used for the temporary storage of data and program instructions in microprocessor-based systems. 41

41 Summary A typical RAM IC is the 2114A. It is organized as 1k 4, which means that it has 1k locations, with 4 bits of data at each location. (1k is actually represents 2 10 = 1024.) An example of a higher-density RAM IC is the 6206, which is organized as 32k 8. A typical RAM IC is the 2114A. It is organized as 1k 4, which means that it has 1k locations, with 4 bits of data at each location. (1k is actually represents 2 10 = 1024.) An example of a higher-density RAM IC is the 6206, which is organized as 32k 8. 42

42 Summary Dynamic RAMs are less expensive per bit and have a much higher density than static RAMs. Their basic storage element is an internal capacitor at each memory cell. External circuitry is required to refresh the charge on all capacitors every 2 ms or less. Dynamic RAMs are less expensive per bit and have a much higher density than static RAMs. Their basic storage element is an internal capacitor at each memory cell. External circuitry is required to refresh the charge on all capacitors every 2 ms or less. 43

43 Summary Dynamic RAMs generally multiplex their address bus. This mean that the high-order address bits share the same pins as the low-order address bits. They are demultiplexed by the RAS and CAS (Row Address Strobe and Column Address Strobe) control signals. Dynamic RAMs generally multiplex their address bus. This mean that the high-order address bits share the same pins as the low-order address bits. They are demultiplexed by the RAS and CAS (Row Address Strobe and Column Address Strobe) control signals. 44

44 Summary Read-only memory (ROM) is used to store data on a permanent basis. It is nonvolatile, which means that it does not lose its memory contents when power is removed. Read-only memory (ROM) is used to store data on a permanent basis. It is nonvolatile, which means that it does not lose its memory contents when power is removed. 45

45 Summary Three common ROMs are (1) the mask ROM, which is programmed once by a masking process by the manufacturer; (2) the fusible-link programmable ROM (PROM), which is programmed once by the user; and (3) the erasable-programmable ROM (EPROM), which is programmable and UV-erasable by the user. Three common ROMs are (1) the mask ROM, which is programmed once by a masking process by the manufacturer; (2) the fusible-link programmable ROM (PROM), which is programmed once by the user; and (3) the erasable-programmable ROM (EPROM), which is programmable and UV-erasable by the user. 46

46 Summary Memory expansion in microprocessor systems is accomplished by using octal or hexadecimal decoders as address decoders to select the appropriate memory IC. Memory expansion in microprocessor systems is accomplished by using octal or hexadecimal decoders as address decoders to select the appropriate memory IC. The Electrically-Erasable PROM (EEPROM) and Flash memory use a floating-gate MOSFET for their primary storage element. A charge on the floating gate represents the stored data. The Electrically-Erasable PROM (EEPROM) and Flash memory use a floating-gate MOSFET for their primary storage element. A charge on the floating gate represents the stored data. 47

47 Summary Magnetic storage like the floppy or hard disk use magnetized particles to represent the stored 1 or 0. Individual data bits are read and written using an electro-magnetic read/write head. Magnetic storage like the floppy or hard disk use magnetized particles to represent the stored 1 or 0. Individual data bits are read and written using an electro-magnetic read/write head. Optical memory like the CD or DVD use a laser beam to reflect light off of a rigid platter. The CD or DVD platter will either have a non-reflective pit to represent a 1 or a non-pit (land) to represent a 0. Optical memory like the CD or DVD use a laser beam to reflect light off of a rigid platter. The CD or DVD platter will either have a non-reflective pit to represent a 1 or a non-pit (land) to represent a 0. 48


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