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2008 BPM Microsystems Confidential and Proprietary

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Factory Preprogramming Solutions for NAND Flash Devices Dragon Zhang

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2008 BPM Microsystems Confidential and Proprietary What Is Factory Preprogramming? Factory preprogramming is the writing of initial data content into a non-volatile memory device. The memory devices are usually virgin blanks straight from the semiconductor distributor. At the very least, factory preprogramming provides the bootstrapping necessary for the embedded system.

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2008 BPM Microsystems Confidential and Proprietary Example Preprogrammed Content Store-and-download SnD boot loader OS, System Firmware Preloaded user content: Applications Pictures, Music, Movies GPS Maps Unique / Dynamic content: Serial Numbers Network addresses Encryption keys

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2008 BPM Microsystems Confidential and Proprietary The Hidden Added Cost Per Device Devices per Hour (DPH) The number of successfully preprogrammed devices that a process can produce in an hour. Aka Units per Hour. Outsourced Programming Fees Additional charge to preprogram your data. Price depends on DPH and volume. $0.25 - $1.00 per device typical range. Production beat rate

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2008 BPM Microsystems Confidential and Proprietary Factory Preprogramming Methods Offline / In-Socket In-house Outsourced Manual Automated (Pick & Place) ISP / ICP Via Connected Target System Via Test Port (eg JTAG) Via In-circuit test (ICT) system

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2008 BPM Microsystems Confidential and Proprietary Offline In-Socket Performance Advantage Isolated Device Concurrency + Gang Scalable Eliminate failures before solder process Easy to outsource. Or, handle in-house.

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2008 BPM Microsystems Confidential and Proprietary In-Circuit / In-System Its how the design engineers did it. But youll need more than the DevKit. Can you reuse your embedded code? 40+ minute programming times are common

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2008 BPM Microsystems Confidential and Proprietary This Sounds Like Productions Problem Whats all of this have to do with designing flash-based products? Your NAND driver choices will have an impact on the manufacturability of your product. Your decisions on NAND control during the design phase can mean the difference between turn-key factory preprogramming and weeks of delays. It really happens!

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2008 BPM Microsystems Confidential and Proprietary Preprogramming Considerations - NAND Flash Type Is it raw SLC, raw MLC, or managed? If managed, is it consumer card or SMT packaged? Standard or proprietary interface? Huge Device Densities Data Pattern file logistics (Gigabytes) Program Disturbs Data Output Data Input, but not always an error! Bad Block Management

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2008 BPM Microsystems Confidential and Proprietary Raw NAND Types 1.Single-Level Cell (SLC) Fastest NAND Flash No disturbs during preprogramming 2.Multi-Level Cell (MLC) More memory, but less speed, less intrinsic reliability 1-bit disturbs certain, 2-bit likely Preprogramming verification must tolerate a specified number of bit errors or yield will be 0% Raw NAND requires an extra algorithm plug-in for Bad Block Management

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2008 BPM Microsystems Confidential and Proprietary Managed NAND Types 1.Consumer Card CF, SD, MMC, MS 2.Surface Mount Package Embedded eMMC, moviNAND, iNAND Easy to preprogram. No extra algorithms necessary!

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2008 BPM Microsystems Confidential and Proprietary Performance Comparisons

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2008 BPM Microsystems Confidential and Proprietary What is Bad Block Management (BBM)? NAND ships from factory with bad blocks, and a scheme must be employed to deal with that. The system preprogramming the NAND must do it exactly the same as the target system. Its the biggest challenge to ramping up volume preprogramming of NAND. Plan ahead at design time and it wont be a problem at production time.

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2008 BPM Microsystems Confidential and Proprietary Raw NAND Requires 2 Algorithms

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2008 BPM Microsystems Confidential and Proprietary Who specifies the BBM Algorithm? The provider of the FFS software that you integrated? Some undocumented open-source FFS software? The FFS or driver software that you wrote yourself? The MCU/chipset vendor? The NAND Flash vendor? The hardware IP provider? Some combination of the above? The most common answer: I dont know.

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2008 BPM Microsystems Confidential and Proprietary Six BBM Preprogramming Elements 1.Bad Block Replacement Strategy 2.Partitioning 3.Error Correction Codes (ECC) 4.Spare Area Placement 5.Free Good Block Formatting 6.Dynamic Metadata

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2008 BPM Microsystems Confidential and Proprietary Skip Bad Blocks When a bad block is encountered, simply skip ahead to the next good block. No tables, no tags. Simple Suitable for preprogramming and WORM applications. Most FFSs will require more sophistication at runtime. Good Bad

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2008 BPM Microsystems Confidential and Proprietary Reserve Block Area (RBA) A portion of the flash memory is set aside to replace bad blocks. When a bad block is encountered, redirect the data to a replacement block in the RBA, then resume. Usually requires a mapping data structure. Good Bad Good RBA @ End of Device

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2008 BPM Microsystems Confidential and Proprietary Partitioning for SBB Partitioning is required to prevent regions from encroaching on adjacent regions when bad blocks occur. Allows you to guarantee a fixed starting block for IPL, bootloaders, FFS mounts, etc. Block 0 1 1 block 2 blocks 10 blocks 6 blocks 2017 blocks 2 4 5 14 24 25 30 2047 Bootstrap Bootloader OS File System Padding Cleanmarkers

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2008 BPM Microsystems Confidential and Proprietary Partitioning for RBA Defines the User Block Area and Reserve Block Area allocations. Bad blocks dont disrupt the physical location of data on good blocks. 2047 2046 Block 0 1638 blocks 2 blocks 408 blocks 1637 1638 Metadata, BB Table User Block Area 2045 Reserve Block Area

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2008 BPM Microsystems Confidential and Proprietary Specifying Partitioning Specify the details of your NAND partitioning to manufacturing or programming center. Or, use tools that emit partition tables and furnish the file.

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2008 BPM Microsystems Confidential and Proprietary ECC Calculated values that allow for detection and correction of bit errors in the original data. Preprogrammer must write the ECCs exactly as the target system expects. Definitively specifying an ECC algorithm: Hamming, Reed-Solomon, BCH Additional parameters, sub-pages, hybrid schemes Most embedded system designers cannot fully specify the ECC used in their NAND control system. ECCs should be pre-encoded for static data pattern content to boost DPH.

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2008 BPM Microsystems Confidential and Proprietary Spare Area Placement Aka Out-Of-Band (OOB) Area How are the ECC bytes arranged? Bad Block Marker(s) Other metadata 2048 64 BB Marker FFS MetadataECC0ECC1ECC2ECC3ECC4ECC5ECC6ECC7 MainSpare...

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2008 BPM Microsystems Confidential and Proprietary Free Good Block Formatting What to fill the unused good blocks with. For every bad block on the device, one block of FGBF will be discarded. Common Examples: 0xFF / Blank Padding Completely blank pages are not programmed, just blank checked. This is the most common FGBF. JFFS2 Cleanmarkers

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2008 BPM Microsystems Confidential and Proprietary Dynamic Metadata Additional computed data written to the device based on the individual DUT. Includes information such as: Filesystem headers, erase counts, logical-physical mappings, etc. Customized bad block tables Other unanticipated crazy stuff

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2008 BPM Microsystems Confidential and Proprietary Confidentiality and IP Issues Who owns the IP of your BBM algorithm? Many hardware and software vendors will not disclose to you the details of their BBM and/or ECC algorithm. Dont delay your product launch while lawyers execute NDAs. It really happens!

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2008 BPM Microsystems Confidential and Proprietary Universal BBM for Preprogramming 1.BBR: Skip Bad Blocks 2.Partitioning: One or more partitions defined. 3.ECCs: Pre-computed in the data pattern. 4.SAP: All Spare Area bytes in the data pattern. 5.FGBF: All unused block formatting or padding (FFh) in the data pattern. 6.Dynamic Metadata: None! Many commercial, open-source, and proprietary BBMs adhere to this.

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2008 BPM Microsystems Confidential and Proprietary De facto Image File Conventions Flat binary file. 1:1 mapping to devices physical blocks, Main+Spare for each page. Contains full page data, all spare area content, including ECCs, needed for board bring-up. Includes all Free Good Block Formatting, even if its just blank padding.

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2008 BPM Microsystems Confidential and Proprietary NAND Drivers & FFS Considerations Open-Source Ex: Linux JFFS2, UBI Commercial off-the-shelf (COTS) Software Ex: FlashFX, TargetFFS, CMX-FFS Hardware Controller + Software Ex: MSM7201, OMAP3530, Databahn+Spectra One-off / Roll-your-own Determine during the design phase preprogramming support for your FFS.

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2008 BPM Microsystems Confidential and Proprietary BBM Algorithm Plug-ins Generally any BBM algorithm can be combined in the field with any Raw NAND device algorithm. Part number changes are no problem. But beware of one-off or esoteric BBM schemes! If it cant be coded using the defined abstractions, the alternative is to produce a combined BBM+Device algorithm. Higher development costs Longer lead times Cant change the part number in the field.

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2008 BPM Microsystems Confidential and Proprietary Bit Error Rate Tolerance for Raw MLC Before MLC, disturbs were a non-issue with factory- fresh devices. Now with MLC, programming a page will corrupt some bits in another page of the same block. Normally this is a verify failure. But with MLC youll get 0% yield. The preprogrammer must tolerate a certain number of incorrect bits per page during verify. Specify the BERT in bits per page for your application!

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2008 BPM Microsystems Confidential and Proprietary Design Tips Fully specify BBM to production: Six preprogramming elements BERT for Raw MLC Balance yield vs. waste for bad block allowances. Deliver standard image file. If you are designing an FFS, support the use of Skip Bad Blocks Compatible factory preprogramming. FFS vendors can help their customers and increase their products adoptability by adhering to this rule!

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2008 BPM Microsystems Confidential and Proprietary Resources Whitepaper: TODO http://flashstream.bpmmicro.com http://www.bpmmicro.com/pdf/FMS2008- WhiteT1BSlides.pdf

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2008 BPM Microsystems Confidential and Proprietary Questions?