Article Details

ID: 2037
Case Type: faq
Category: Device Programming
Related To: Configuration/Programming
Family: 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.