2.4.2.1 Class B Self-Tests

The various Class B self-tests implemented on FSFEB are:

  • SRAM test
  • CRC test
  • Button test

SRAM Test

On start-up, the device will run a test of the internal SRAM. The purpose of the test is to detect stuck bits and coupling faults in SRAM and on the data bus, and any addressing problems. The internal SRAM is used for volatile storage of data, and any faults related to this can cause issues for the appliance control.

CRC Test

On start-up, the device will run a CRC test to determine if Flash content is unchanged, by calculating a checksum and comparing this to a checksum programmed at the end of Flash. The CRC test will also be run once every second after start-up. The purpose of the test is to detect changes in Flash as soon as they happen and take action to stop the device from executing potentially wrong Flash content.

Button Test

On start-up, the device will check all three buttons on FSFEB if they are pressed down or not. If a button is pressed down, the class B self-test fail LED will be turned ON. The purpose of the test is to determine if the buttons are broken or not.
Note: If all three buttons are pressed down during start-up, FSFEB will enter calibration mode.

To be able to get the Class B pass LED to turn ON, all Class B self-tests must pass. If any of the tests fail, the class B fail LED will turn ON.