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AT42QT1111-AU Datasheet(PDF) 19 Page - ATMEL Corporation |
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AT42QT1111-AU Datasheet(HTML) 19 Page - ATMEL Corporation |
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19 / 50 page  19 AT42QT1111-MU / AT42QT1111-AU [DATASHEET] 9571C–AT42–05/2013 4.9 Guard Channel Option The device has a guard channel option (available in all key modes), which allows one key to be configured as a guard channel to help prevent false detection (see Figure 4-9 on page 19). Guard channel keys should be more sensitive than the other keys (physically bigger or larger Cs), subject to burst length limitations (see Section 4.11.2 on page 20). With guard channel enabled, the designated key is connected to a sensor pad which detects the presence of touch and overrides any output from the other keys using the chip AKS feature. The guard channel option is enabled by the Guard Key setup byte (see Section 7.5 on page 29). With the guard channel not enabled, all the keys work normally. Note: If a key is already “in detect” when the guard channel becomes active, that key will remain in detect and the guard key will not activate until the active key goes out of detect. Figure 4-9. Guard Channel Example 4.10 Self-test Functions 4.10.1 Internal Hardware Tests Internal hardware tests check for hardware failure in the device internal memory areas and data paths. Any failure detected in the function or contents of application ROM, RAM or registers causes the device to reset itself. The application code is scanned with a CRC check routine to confirm that the application data is all correct. The RAM and registers are checked periodically (every 10 seconds) for dynamic and static failures. 4.10.2 Functional Checks Functional checks confirm that the device is operating within expected parameters; any failure detected in these tests is notified to the system host. The device will continue to operate in the event that such functional failures are detected. The functional tests are: Check that the channel-measurement signals are within the defined range. Confirm that data stored in the EEPROM is valid. These tests are carried out as the particular functions are used. For example, the EEPROM is checked when the device attempts to load data from EEPROM, and the channel signals are checked when a measurement is carried out. Note: If a particular channel is unused, the threshold of that channel should be set to 0 to prevent the incorrect reporting of the unused channel as being in an error state. Guard Channel Formed of One Key Key Pad Formed of Six Keys |
Similar Part No. - AT42QT1111-AU_14 |
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Similar Description - AT42QT1111-AU_14 |
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