at42qt1481 ATMEL Corporation, at42qt1481 Datasheet - Page 7

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

2.2
2.3
9621B–AT42–06/11
Matrix Scan Sequence
Enabling/Disabling Keys – Burst Paring
The circuit operates by scanning each key sequentially. The keys are numbered from 0 – 47.
Key scanning begins with location X = 0, Y = 0 (key 0). All keys on X0 are scanned first, then X1
and finishing with all keys on X7 (for example, the sequence X0Y0, X0Y1 – X0Y5, X1Y0,
X1Y1...).
Table 2-1.
All keys on the same X line are excited together in a burst of acquisition pulses whose length is
determined by the Setups parameter BL (see
different value for each key. A burst is completed entirely before the next X line is excited. At the
end of each burst the resulting signals, one for each Y line, are converted to digital form and
processed. The burst length directly impacts key gain. Each key can have a different burst
length in order to allow tailoring of key sensitivity.
Unused keys are always pared from the computation sequence in order to optimize speed. If all
keys are disabled on any given X, the entire X line is also pared from the burst sequence. If only
two X lines have enabled keys, only two timeslots are used for scanning.
The NDIL parameter is used to enable and disable keys in the matrix. Setting NDIL = 0 for a key
disables it
sequence to save scan time and thus power. If all keys on an X line are disabled, the burst for
the entire X line is removed from the scan sequence, further saving time and power. This has
the consequence of affecting the scan rate of the entire matrix as well as the time required for
initial matrix calibration. It does not affect the time required to calibrate an individual key once
the matrix is initially calibrated after power-up or reset.
Y0
Y1
Y2
Y3
Y4
Y5
Table 2-1
(Section 5.5 on page
X7
15
23
31
39
47
7
Key Numbers
shows the key numbering.
X6
14
22
30
38
46
6
X5
13
21
29
37
45
5
42). Keys that are disabled are eliminated from the scan
X4
12
20
28
36
44
4
Section 5.9 on page
X3
11
19
27
35
43
3
X2
10
18
26
34
42
2
X1
17
25
33
41
1
9
44); this can be set to a
AT42QT1481
X0
16
24
32
40
0
8
numbers
Key
7