qt60248 Quantum Research Group, qt60248 Datasheet - Page 14

• Manufacturer Part Number: qt60248
• Description: 16, 24 Key Qmatrix? Ics
• Manufacturer: Quantum Research Group

4.15 Data Set for One Key - 0x4k
Returns the data set for key k, where k = {0..23} encoded into
the low nibble of this command. This command returns 5 bytes,
in the sequence:
Signal and Reference are returned LSByte first. No CRC is
appended.
Keys that are disabled report ‘0’ for both signal and reference.
4.16 Status for Key ‘k’ - 0x8k
Returns a bitfield for key ‘k’ where k is from {0..23}. The bitfield
indicates as follows:
Bit 2 - LSL notes: See page 21.
A CRC byte is appended to the response; this CRC folds in the
command 0x8k itself initially.
Disabled Keys: A disabled key never reports as being in
detect, but always reports an LSL error (if LSL >0). An LSL error
flag generated for this reason is not reflected elsewhere, for
example via the 0x05 or 0x06 commands. An LSL error on an
enabled key is however reflected in the 0x05 and 0x06
commands.
A disabled key also reports back with bit 0 high (failed Cal). A
Cal error flag generated for this reason is not reflected
elsewhere, for example via the 0x05 or 0x06 commands. A Cal
error on an enabled key is however reflected in the 0x05 and
0x06 commands.
Just after reset or after a CAL command (commands 0x03 or
0xCk), a disabled key will report back as being in calibration for
only one matrix scan cycle, then will report as having failed cal.
See also Section 2.2.
4.17 Cal Key ‘k’ - 0xck
This command must be repeated 2x within 100ms or the
command will fail; the repeating command must be sequential
without any intervening command.
lQ
Signal (2 bytes)
Reference (2 bytes)
Normal Detect Integrator (1 byte)
BIT
7
6
5
4
3
2
1
0
Description
1= reserved
1= reserved
1= reserved
1= key is enabled
1= key is in detect
1= signal ref < LSL (low signal error)
1= this key is in cal
1= cal on this key failed 5 times
14
This command functions the same as 0x03 CAL command
except this command only affects one key ‘k’ where ‘k’ is from 0
to 23.
The chosen key ‘k’ is recalibrated in its native timeslot; normal
running of the part is not interrupted and all other keys operate
correctly throughout. This command is for use only during
normal operation to try to recover a single key that has failed or
is not calibrated correctly.
Returns the 1’s compliment of 0xck just before the key is
recalibrated.
4.18 Command Sequencing
To interface the device with a host, the flow diagram of Figure
4-1, page 15, is suggested. The actual settings of the Setups
block used should normally just be the default settings except
where changes are specifically required, such as for sensiti vity,
timing, or AKS changes.
The circles in this drawing are communications interchanges
between host and sensor. The rectangles are internal host
states or processing events. If any communications exchange
fails, either the device will fail to respond within the allotted time,
or the response CRC will be incorrect, or the response will be
out of context (the response is clearly not for the intended
command). In these cases the host should just repeat the
command.
The control flow will spend 99% of its time alternating between
the two states within the dashed rectangle. If a key is detected,
the control flow will enter ‘Key Detection Processing’.
Stuck Key Detection processing (0xCk) is optional, since the
device contains the max on-duration timeout function and can
therefore recalibrate the stuck key automatically. However, the
host can recalibrate stuck keys with greater flexibility if the
recalibration timeouts are set to infinite and the host recalibrates
them under specific conditions.
Error handling takes place whenever an error flag is detected,
or the device stops communicating (not shown). The error
handling procedure is up to the designer, however normally this
would entail shutting down the product if the error is serious
enough (for example, a key that will not calibrate, or a FMEA
class error).
An eeprom CRC error report is serious, and requires that the
host reload the Setups table into the device and thereafter issue
a reset command or hardware reset.
The ‘Last Command’ command can be used at any time to clear
comms error flags and to resynchronize failed communications,
for example due to timing errors etc.
QT60248-AS R4.02/0405