NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
- 1247 -
Revision V1.30
NUC97
0
T
E
CHNIC
A
L
RE
F
E
RE
N
CE
MA
NUA
L
Pre-Scale Divider (KPIPRESCALDIV)
Register
Offset
R/W
Description
Reset Value
KPIPRESCALDIV
0x28
R/W
Pre-Scale Divider
0x0000_001F
31
30
29
28
27
26
25
24
Reserved
23
22
21
20
19
18
17
16
Reserved
15
14
13
12
11
10
9
8
Reserved
7
6
5
4
3
2
1
0
PRESCALDIV[7:0]
Bits
Description
[31:8]
Reserved
Reserved.
[7:0]
PRESCALDIV
Pre-scale Divide
This value is used to divide PRESCALE that is set in KPICONF[15:8]. The Prescale
divider counter is clocked by the divided crystal clock, xCLOCK. The pre-scale divider
number is from 1 to 256.eg.If the crystal clock is 1Mhz then the xCLOCK period is 1us. If
the keypad matrix is 3x3 then
Each row scan time = xCLOCK x PRESCALE x PrescaleDivider.
Key array scan time = Each row scan time x ROWS.
Example scan time for PRESCALE = 0x41,and PrescaleDivider = 0x1F.
Each row scan time = 1us x 65 x 32 = 2.08ms.
Scan time = 2.08 x 3 = 6.24ms.
Notes:
When PRESCALE (KPICONF[15:8]) is determined, De-bounce sampling cycle
should not exceed the half of (PRESCALE x PrescaleDivider ),in the above example
maximum DBCLKSEL (KPICONF[19:16]) should be 4*256 xclock ,bouncing time is 1ms