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ID: 2037
实例类型: faq
分类: Device Programming
相关: Configuration/Programming
产品系列: All CPLD

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What are the last four characters in the JEDEC file of a Lattice CPLD ?

The last four characters represent the transmission checksum of the JEDEC file. This checksum is calculated from design checksum and the headers. Therefore anything different in the file, such as the date / time of compilation, will result in a different transmission checksum.


This transmission checksum is defined by the JESD-3C standard. It is simply the sum of all of the ASCII contents of the file,from start of the text to end of the text, including notes, whitespace, fuse values, and other characters. Since the JEDEC file will typically have notes that contain the time and date of its creation, the transmission checksum will generally be different for the same design even if the fuse contents are the same.


For example:


random text <return><line feed>                                              = 0000


<STX>TEST*<return><line feed> 02+54+45+53+54+2A+0D+0A        = 0183


QF0384*<return><line feed> 51+46+30+33+38+34+2A+0D+0A          = 01A7


F0* <return><line feed>       46+30+2A+20+20+0D+0A                     = 00F7


L10 101* <return><line feed> 4C+31+30+20+31+30+31+2A+0D+0A = 01A0


<ETX>05C4<return> random text  03                                                =0003


total                                                                                                 = 05C4


This is the transmission checksum.