at42qt1481 ATMEL Corporation, at42qt1481 Datasheet - Page 17

• Manufacturer Part Number: at42qt1481
• Description: 48-key Qmatrix Ic
• Manufacturer: ATMEL Corporation

2.18
9621B–AT42–06/11
EN60730 Compliance
Also, since the QT1481 only communicates in slave mode, the host can determine immediately
if the QT1481 has suffered a catastrophic failure. The QT1481 can also participate in
cross-checking the integrity of the host controller, and even reset the host if no communications
have been heard from it in a short while (via the STATUS pin output).
The FMEA tests performed are:
Other tests incorporated into the QT1481 include:
The QT1481 also incorporates special test features which, together with the FMEA tests, allow
products to achieve EN60730 compliance with ease. EN60730 compliance demands dynamic
verification of all safety related components and sub-components within a product. The QT1481
is able to verify some sub-components internally, but others require verification by a separate,
independent processing unit with another timing source.
To this end the QT1481 exposes a number of internal operating parameters through its serial
communications interface and requires the cooperation of a host to check and verify these
parameters regularly. It is also necessary for the host to verify the communications by checking
and validating the CRC, which the QT1481 appends to data returns. If a CRC check should fail,
the host should not rely on the data but retry the transmission.
Occasional CRC failures might be anticipated as a result of noise spikes. Repeated CRC
failures might indicate a safety-critical failure. Where the QT1481 is able to verify
sub-components internally, but any such verification fails, the QT1481 disables serial
communication and locks up in an infinite loop. The host can detect this condition if repeated
CRC failures are observed.
During normal operation the host must perform regular reads of the EN60730 counters (see
Section 4.7 on page
regular reads of the QT1481 status (see
reported. The FMEA error flag, LSL error flag and Setups CRC error flag must all be considered
as part of an EN60730 compliant design.
• X drive line shorts to Vdd and Vss
• X drive line shorts to other pins
• X drive signal deviation
• Y line shorts to Vdd and Vss
• Y line shorts to other pins
• X to Y line shorts
• Cs capacitor checks including shorts and opens
• Vref test
• Key gain (see
• A test for signal levels against a preset minimum value (Lower Signal Limit (LSL) setup, see
• 16-bit CRC communications checks on all data returns.
• “Last-command” command to verify that an instruction was properly received.
• Loss of communications reset of the host controller.
Section 5.18 on page
Section 5.19 on page
28) to verify correct operation of the QT1481. The host must also perform
48). If any signal level falls below this level, an error flag is generated.
48)
Section 4.7 on page
28) and verify there are no errors
AT42QT1481
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