VOICE OF THE ENGINEER - ElectronicsAndBooks

More documents

Recommendations

Info

Surface Mountand Plug-In400 / 800 HzTransformersNow...up to150Watts• 0.4 Watts to 150 WattsPower Transformers• 115V/26V-400/800 Hz Primary• Secondary Voltages2.5V to 300V• Manufactured to MIL-PRF 27Grade 5, Class S, (Class V,155 0 C available)• Surface Mount or Plug-In• Smallest possible sizeSee Pico’s full Catalog immediatelywww.picoelectronics.comPICOElectronics, Inc143 Sparks Ave., Pelham, NY 10803Call Toll Free: 800-431-1064E Mail: info@picoelectronics.comFAX: 914-738-8225Delivery - Stock to one weekINDUSTRIAL • COTS • MILITARYEXTERNALNAND-FLASHMEMORYINTERNALFLASHPROCESSORNAND-FLASHCONTROLLERSYSTEM ON CHIPallow a system to boot from a variety ofinterfaces (Figure 7). Booting from internalflash memory is among the mostcommon and simplest methods of configuringan embedded microcontrollerthat includes the necessary on-chip resources.This method reduces dependencieson external interfaces becausethe boot loader resides in on-chip memory.After system-reset deassertion, theprocessor points to the flash memory’sstarting address and loads the necessaryinitialization code and operatingsystems. Operating systems with smallfootprints arecompatible withthis approach becausea practicallimit exists on theamount of on-chipflash memory thatcan be available.This approach isalso one of mostsecure ways to boot a processor becausemodifying code residing in on-chipmemory requires fewer changes than dooff-chip boot options.As with Windows XP, some microcontrollersintegrate ROM as the primaryboot option. The boot ROM includesa basic boot loader so that the microcontrollercan subsequently perform amore sophisticated boot sequence onits own, loading programs from varioussources, such as Ethernet, NAND-flashmemory, an SD (secure-digital) card,an MMC (multimedia card), or a USBinterface. Boot-ROM usage enablesmore flexible boot sequences than doesSYSTEMMEMORYEXTERNAL-BUSEXTERNALINTERFACE FLASHCHIP SELECTBOOTROMDRAMCONTROLLERDDRMEMORYFigure 7 Common hardware-boot components allow a system to boot from a variety ofinterfaces.AS WITH WINDOWS XP,SOME MICROCON-TROLLERS INTEGRATEROM AS <strong>THE</strong> PRIMARYBOOT OPTION.hard-wired logic, and it allows usersthe choice to boot up from various peripherals.Users often employ the boot-ROM feature for system recovery whensomeone inadvertently erases the usualboot software in nonvolatile memoryother than ROM. You cannot reprogramboot ROM, so applications thatrequire a secure boot may include securitychecks so that the boot-up stops ifone or multiple security checks fails.An external bus interface allows thesystem to boot directly from externalNOR flash or other parallel memories.It is one ofthe fastest waysto boot the systembecause theinterface to externalmemorycan be 32 bits ormore with a reasonablefrequencyof operation. Fora full-fledged operating system such asLinux, or Windows, it can take severalmilliseconds to seconds to boot the systemdue to the size of the operating system,which can be annoying to the user.Keeping the boot loader/operating systemin external parallel memory reducesthe boot-up time drastically for systemsin which boot time is critical.NAND-flash memories are gainingpopularity in numerous applications dueto their higher read throughput, althoughthis throughput is lower than that ofNOR-flash memory. NAND flash alsooffers faster erases and lower cost per bytethan does NOR flash. The primary use
EXTERNALNAND MEMORYOPERATING-SYSTEMCODEPROCESSORNAND-FLASHCONTROLLERSYSTEM ON CHIPfor NAND-flash memory—for example,in a USB flash drive—is to store largequantities of data and code. However,in recent years, an increasing number ofembedded-system applications also supportNAND-flash memory as a primaryboot option. In these cases, the microcontrollermust include a NAND-flashmemorycontroller to handle read andwrite accesses. The NAND-flash-memoryinterface also requires more than 20pins, so this option may not be cost-effectiveand otherwise practical unlessyou use a package with more pins.Booting from internal volatile memoryis always a secondary boot techniquebecause a primary boot device mustload the RAM before it can executecode. Commonly, a primary boot loadsthe operating system and drivers, copyingthem to RAM. At this point, theRAM-based code takes control of thesystem. Executing code from RAM isfaster and consumes less power than doother memory technologies, includingeither external or internal flash memory.However, because the internal RAMis volatile, some system designs enablethe RAM to switch to battery power inthe event of the failure of the primarysupply, thereby eliminating any furtherneed to copy the code from externalor internal memory when the primarypower returns and thus reducing subsequentinitialization and boot time.Booting from a DRAM is also a secondaryboot technique. DRAM use iscommon in high-end applications thatmust handle abundant multimedia contentand that require high throughput.You can view DRAM as a bigger andfaster extended RAM buffer for managingcomplicated applications. In one example,ROM includes the boot loader,and NAND-flash memory contains theoperating system and the applicationBOOT ROMBOOT LOADERDRAMCONTROLLERDDRMEMORYOPERATING-SYSTEMEXECUTIONFigure 8 Secondary boot using high-performance DRAM requires a correspondingnonvolatile primary-boot device, such as a ROM or a flash memory.code (Figure 8). The boot process beginswith system initialization through theROM-boot loader, which also includesthe reset vector. The main operatingsystemcode copies from NAND-flashmemory to DDR SDRAM, subsequentlyswitching execution control to the externalvolatile memory. This scheme isefficient because executing from DDRSDRAM is faster than reading directlyfrom NAND-flash memory. You can usesimilar schemes to copy code from otherinterfaces, such as Ethernet.You may want to boot from variousinterfaces, such as SDHC, SPI, I 2 C (inter-integratedcircuit), USB, SATA (serialadvanced-technology attachment),PCIe, and Ethernet. These interfaces allrepresent secondary boots. A primaryboot interface, such as ROM, initializesa secondary boot interface, such asUSB, before code execution switchesto the secondary boot device. Storingboot code in external nonvolatile serialmemories, such as SPI flash memoryor I 2 C EEPROM, can be useful for microcontrollersthat have low pin countsand can afford to have longer boot-ups.Such schemes first copy the boot codefrom the external memory to the onchipRAM and code execution switchesto the RAM after reset, so the schemecan immediately fetch boot code afterreset deassertion.EDNAUTHORS’ BIOGRAPHIESMohit Arora is a systems engineer at FreescaleSemiconductor. He has a bachelor’sdegree in electronics and communicationsengineering from Netaji Subhas Instituteof Technology (New Delhi, India).Varun Jain is a senior design engineer atFreescale Semiconductor. He has a bachelor’sdegree in engineering from Delhi Collegeof Engineering (Delhi, India).NewHighVoltageUp to 500 VDCHi PowerUp to 50 WattsRegulatedDC-DCConvertersMiniaturizedSize Package:2.5" X 1.55" X 0.50"High Voltage, Isolated Outputs100-500 VDCLow Voltage Isolated Outputs5-48VDC also StandardQP SeriesIsolatedOutput Voltages from 500VDCHigh Power: to 50 Watts,Efficiency to 90%5, 12, 24, Wide Input RangesConsult Factory for Special InputVoltagesSafe: Short Circuit, Over/UnderVoltage, and Over Temp. ProtectedOptions Available: ExpandedOperating Temperature, -55 0 C to +85 0 CEnvironmental Screening, Selectedfrom MIL Std.883Ruggedized for Operation inHarsh EnvironmentsExternal Bias Control: For ChargePump ApplicationsCustom Modules: Available tooptimize your designs, SpecialInput or Output Voltages AvailablePICO’s QP Series compliments our 650plus existing standard High VoltageModules. Isolated, Regulated,Programmable, COTS and CustomModules available, to 10,000 VDC andother High Voltage to 150 Watts!www.picoelectronics.comE-Mail: info@picoelectronics.comFAX 914-738-8225PICO Electronics,Inc.143 Sparks Ave, Pelham, NY 10803-1837
Page 1 and 2: VOICE OF THE ENGINEERFEB3Issue 3/20
Page 3 and 4: VOICE OF THE ENGINEERFEB3Issue 3/20
Page 7 and 8: 2.3.11contentsAdvances inenergy-sto
Page 9 and 10: contents2.3.11Simpler PowerConversi
Page 11 and 12: ASSOCIATE PUBLISHER,EDN WORLDWIDEJu
Page 13 and 14: Analog Devices: enabling the design
Page 15 and 16: Class D amplifier suppresses EMISil
Page 17 and 18: SIGNAL INTEGRITYBY HOWARD JOHNSON,
Page 19 and 20: with more sophistication. The boot
Page 21 and 22: loop) to achieve clock locking befo
Page 23: CLOCKRESETCONFIGURATIONSERIALBOOTLO
Page 27 and 28: ENERGY HARVESTING RELIES ONINTERMIT
Page 29 and 30: Have you heard?Oscilloscopes fromth
Page 32 and 33: POWER CONSTRAINTS OF WIRELESS SENSO
Page 34 and 35: Your Project Acceleration Resource
Page 36 and 37: BY ALLAN EVANS • SAMPLIFY SYSTEMS
Page 38 and 39: The voltage required across the sup
Page 40 and 41: SENSORSORARRAYRAYADCMULTI-CHANNELAD
Page 42 and 43: 5A LDO for Digital ICs85mVDropoutVo
Page 45 and 46: Get an edge: laser driversPhoto Cou
Page 47 and 48: YOU CAN IMPROVETHE CIRCUIT BYREPLAC
Page 49 and 50: or even destroy a power supply’s
Page 51 and 52: IntroducingEDN’s NewMicrosite on
Page 53 and 54: ADVERTISER INDEXCompany Page Compan
Page 55 and 56: www.globalfoundries.com/mwc

VOICE OF THE ENGINEER - ElectronicsAndBooks

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?