Datasheet

4
9502A–AT42–07/08
AT42QT2160
Figure 3-1. Field Flow Between X and Y Elements
3.1 Keys and Slider
The QT2160 is capable of a maximum of 16 keys. These can be located anywhere within an
electrical grid of 8X and 2Y scan lines.
A lesser number of enabled keys will cause any unused acquisition burst timeslots to be pared
from the sampling sequence, to optimize acquire speed and lessen power consumption. Thus, if
only 8 keys are actually enabled, only 8 timeslots are used for scanning.
Additional processing can be done on the keys to form a slider. The slider will have to start at X0
and use only Y0. The slider can consist of a minimum of 2 keys and a maximum of 8 keys.
3.2 Enabling/Disabling Keys
Keys can be enabled by setting a nonzero burst length. A zero burst length disables the key.
4. Hardware and Functional
4.1 Matrix Scan Sequence
The circuit operates by scanning each key sequentially, key by key. Key scanning begins with
location X = 0, Y = 0 (key 0). X axis keys are known as rows while Y axis keys are referred to as
columns although this has no reflection on actual wiring. Keys are scanned sequentially by row,
for example the sequence X0Y0 X1Y0...X7Y0, X0Y1, X1Y1... etc. Keys are also numbered from
0...15. Key 0 is located at X0Y0. Table 4-1 shows the key numbering.
Table 4-1. Key Numbers
Each key is sampled in a burst of acquisition pulses whose length is determined by the Setups
parameter BL (Section 4.2 on page 5); this can be set on a per-key basis. A burst is completed
entirely before the next key is sampled; at the end of each burst the resulting signal is converted
to digital form and processed. The burst length directly impacts key gain; each key can have a
unique burst length in order to allow tailoring of key sensitivity on a key-by-key basis.
overlying panel
X
element
Y
element
X7 X6 X5 X4 X3 X2 X1 X0
Y0 76543210
Key numbers
Y1 15 14 13 12 11 10 9 8