Keep alive patterns prevent interference with clocks and PLLs during certain actions in the Digital Pattern Editor. Use them to maintain stability while performing other tasks.

Select File » New or click the Add Item button Add Item on the Project Explorer window toolbar to create a new document. Double-click a .digipat file in the Project Explorer window or right-click the file and select Open from the context menu to launch the pattern document. The toolbar for a keep alive pattern includes only buttons relevant to keep alive patterns. The keep alive pattern document includes a status indicator and a Keep Alive Pattern indicator.
Examples for tasks you can perform using keep alive patterns:
  • Loading or unloading patterns
  • Changing time sets
  • Configuring digital instruments
  • Switching between tests in the test program

To burst a keep alive pattern, first load the keep alive pattern. Then, burst a standard pattern that jumps to the keep alive pattern.

To switch to a keep alive pattern from a standard pattern, use the keep_alive opcode.t You must use the keep_alive opcode on the last vector of a keep alive pattern. This action loops the keep alive pattern until you burst another pattern or abort the keep alive pattern. You can load or unload only one keep alive pattern onto or from the digital pattern instrument at a time.

History RAM results remain unchanged while the keep alive pattern executes. This standard applies to scenarios where a standard pattern jumps to a keep alive pattern.

Note If the keep alive pattern does not use all the pins from the previously executed standard pattern, the unused pins maintain their previous state.
Note To maintain the active status of a pin used in a keep alive pattern, you must also use the pin in subsequent patterns. This requirement applies to patterns that the keep alive pattern can jump to. Consider a pin named CLK_OUT, where the keep alive pattern drives CLK_OUT as a 10 MHz clock. You must use and toggle CLK_OUT in subsequent patterns to ensure that the 10 MHz clock continues toggling during a pattern burst. Without explicitly using this pin, the 10 MHz clock might not maintain its toggling state in the next pattern.