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MachXO2 Programming and Configuration Usage Guide
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Caution when using the above process flow:
Since a Global Reset is triggered during device wake-up after Refresh instruction is issued, attention needs to be
given in designing I/O with following conditions:
• Register output pins
• Impact on the system board level when value changes (may shut off the board, for instance)
• Register is set/reset by global reset
For the I/O in the example above, the state of the I/O is not changed during the TransFR refresh, but may change
once the device gets into user mode right after the TransFR refresh. Following are design tips to avoid this:
• For critical I/Os, try not to use global reset
• For critical I/Os, if you have to use global reset, try to use the set/reset option so that when GSR occurs, the state
of the I/O pin will not trigger a system crash.
Software Selectable Options
The operation of the MachXO2 configuration logic is managed by options selected in the Diamond design software.
Other FPGAs provide dedicated I/O pins to select the configuration mode. The MachXO2 uses the non-volatile
Feature Row to select how it will configure. The Feature Row’s default state needs to be modified in almost every
design. You use the Diamond Spreadsheet View to make the changes to the operation of the MachXO2 Feature
Row which alters the operation of the configuration logic.
The configuration logic preferences are accessed using Spreadsheet View. Click on the Global Preferences tab,
and look for the sysCONFIG tree. The sysCONFIG section is shown in Figure 17. The sysCONFIG preferences are
divided into three categories:
• Configuration mode and port related
• Bitstream generation related
• Security related