Semiconductor, Magnetic and Optical Memory Chapter 16 Semiconductor, Magnetic and Optical Memory William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Memory Concepts Memory locations have memory addresses Data are the memory contents 8 bits known as a byte See Figure 16-2 - Logic Diagram See Figure 16-3 - Timing Requirements William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Figure 16-2 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Figure 16-3 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Static RAMs Random-Access Memory Read/Write Memory Temporary storage of data User can access data at any location randomly CD player or Hard Disk Static or Dynamic William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Static RAMs Static Dynamic use flip-flops as basic storage elements use capacitors as basic storage elements need additional refresh circuitry can be densely packed lower cost per bit William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Static RAMs The 2147H Static MOS RAM 4096 memory locations 4K = 4 x 1024 each location can contain 1 bit 4096 unique addresses needs 212 = 4096 address lines A0 to A5 identify rows A6 to A11 identify columns William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Static RAMs The 2147H Static MOS RAM row and column circuitry pinpoint the memory cell Row Select Column Select uses three-state buffers See Figure 16-6 read cycle write cycle William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Figure 16-6 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Static RAMs Memory Expansion using multiple chips to get more memory capacity See Figure 16-7 - eight 4K chips William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Figure 16-7 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Dynamic RAMs Require more support circuitry More difficult to use Less expensive per bit Higher density, minimizing circuit-board area Usually multiplex address lines Capacitor refreshed during refresh cycle William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Dynamic RAMs Refresh cycle timing Dynamic RAM Controllers usually every 2 ms or sooner Dynamic RAM Controllers developed to simplify the tasks Intel 3243 See Figure 16-12 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Figure 16-12 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Read-Only Memories Store data on a permanent basis Nonvolatile EPROM erasable-programmable-read-only memory Stores operating systems table look-ups language compilers William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Read-Only Memories Mask ROMs Fusible-Link PROMs one-time fee to design a unique mask very inexpensive after one-time fee Fusible-Link PROMs avoid one-time fee every memory cell has a fusible link burned open to permanently store data PROM programmer or MDS William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Read-Only Memories EPROMs EEPROMs can change the memory contents expose an open window to ultraviolet light slowest erasure time EEPROMs non-volatile erased while still in circuit individual bits erased William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Read-Only Memories Flash Memory Floating-gate MOSFET used faster access times erase entire blocks quickly digital cameras and PDAs Floating-gate MOSFET used charge remains on gate for 10 years OTP (one-time-programming) Timing requirements must be met William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Read-Only Memories See Table 16-4 See Figure 16-19 Summary of Semiconductor Memory See Figure 16-19 read cycle write cycle William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Figure 16-19 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Memory Expansion and Address Decoding Applications to identify which IC is to be read or written to See Figure 16-20 16K-byte EPROM (4 x 4K) A PROM Look-Up Table See Application 16-1 A Digital LCD Thermometer See Application 16-2 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Figure 16-20 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Figure 16-23 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Magnetic and Optical Storage Electro-mechanical in nature Non-volatile Magnetic north-south or south-north polarities Optical pits and lands read by a laser system Slower and bulkier but less expensive and higher storage capacities William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Magnetic and Optical Storage Magnetic Memory; The Floppy Disk and Hard Disk magnetizable medium rigid plastic jacket Floppy 300 rpm two read/write heads (one each side) 1.44 MB removable transfer rates of 45KB/sec William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Magnetic and Optical Storage Magnetic Memory; The Floppy Disk and Hard Disk Hard Disk not removable rigid platters sealed unit several two-sided platters one read/write head for each platter surface thousands of rpms Gigabytes of storage capacity William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Magnetic and Optical Storage Magnetic Memory; The Floppy Disk and Hard Disk Hard Disk controlled internal environment bits closely packed concentric circles called tracks (cylinders) 20,000 tracks per inch 300K bits per inch on each track transfer rates of 30 MB/sec William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Magnetic and Optical Storage Magnetic Memory; The Floppy Disk and Hard Disk Removable Hard Disks Zip disk 300 rpm 100 MB Jaz cartridge two rigid platters 2 GB William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Magnetic and Optical Storage Optical Memory CD not as fast as hard disks removable 650 MB aluminum alloy coating rigid polycarbonate wafer pits = 1 lands = 0 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Magnetic and Optical Storage Optical Memory CD one track starting at center and spiraling outward 16,000 tracks per inch thin plastic coating to protect land reflects light, pit does not CD-R photosensitive dye on reflective gold layer laser super heats spot and it will not reflect cannot be erased or re-written William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Magnetic and Optical Storage Optical Memory CD-RW silver alloy crystalline structure laser superheats to amorphous state (non-reflective) laser can reheat at lower level to turn back into crystalline state reflective and non-reflective areas William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Summary A simple 16-byte memory circuit can be constructed from 15\6 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. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

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. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Summary A typical RAM IC is the 2114A. It is organized as 1K x 4, which means that it has 1K locations, with 4 bits of data at each location. (1K is actually an abbreviation for 1024.) An example of a higher-density RAM IC is the 6206, which is organized as 32K x 8. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

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. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

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. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

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. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

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. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Summary 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. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

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. 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. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.