Si3220/Si3225
IQ1
IQ2
IQ5
IQ6
Input
Signal
ILONG
Digital
LPF
+
–
Debounce
Filter
Processor
LONGHI
LONGLPF
LONGDBI
Interrupt
LONGS
LFS
Logic
Ground Key
Threshold
LONGE
LONGHITH LONGLOTH
Figure 22. Ground Key Detection Circuitry
Table 27. Register and RAM Locations Used for Ground Key Detection
Register/
RAM
Register/RAM
Bits
Programmable
Range
LSB
Size
Resolution
Parameter
Mnemonics
Ground Key Interrupt
Pending
IRQVEC2
LONGS
LONGE
LFS[2:0]
Yes/No
Yes/No
N/A
N/A
N/A
N/A
N/A
N/A
Ground Key Interrupt
IRQEN2
Enable
Ground Key Linefeed
Shadow
LINEFEED
Monitor only
Ground Key Detect Status
LCRRTP
LONGDBI
LONGHI
LONGDBI[15:0]
Monitor only
0 to 40.96 s
N/A
1.25 ms
N/A
1.25 ms
Ground Key Detect
Debounce Interval
Longitudinal Current Sense
ILONG
ILONG[15:0]
Monitor only
See Table 20
Ground Key Threshold
LONGHITH
LONG-
0 to
3.097 µA
3.097 µA
N/A
396.4 µA
(enabled)
HITH[15:0]
101.09 mA*
Ground Key Threshold
(released)
LONGLOTH
LONGLPF
LON-
0 to
396.4 µA
GLOTH[15:0]
101.09 mA*
Ground Key Filter Coeffi-
LONGLPF[15:3]
0 to 4000h
N/A
cient
*Note: The usable range for LONGHITH and LONGLOTH is limited to 16 mA. Setting a value > 16 mA will disable
threshold detection.
Rev. 1.0
45
SILICONIMAGE [ Silicon image ]
