PRELIMINARY
CY8C20111, CY8C20121
Document Number: 001-53516 Rev. **
Page 14 of 34
7.10 CS_OTH_SET
CapSense Clock Select, Sensor Auto Reset Register
CS_OTH_SET: 51h
(Writable only in Setup mode)
The registers set the CapSense module frequency of operation and enables or disables the sensor auto reset.
CS_CLK bits provides option to select variable clock input for the CapSense block. A sensor design having higher paratactic requires
lower clock for better performance and vice versa.
Sensor Auto Reset determines whether the baseline is updated at all times or only when the signal difference is below the noise
threshold. When set to ‘1’ (enabled), the baseline is updated constantly. This setting limits the maximum time duration of the sensor,
but it prevents the sensors from permanently turning on when the raw count suddenly rises without anything touching the sensor. This
sudden rise can be caused by a large power supply voltage fluctuation, a high energy RF noise source, or a very quick temperature
change. When the parameter is set to ‘0’ (disabled), the baseline is updated only when raw count and baseline difference is below
the noise threshold parameter. This parameter may be enabled unless there is a demand to keep the sensors in the on state for a
long time. This parameter is common for all sensors.
7.11 CS_HYSTERISIS
Hysteresis Register
CS_HYSTERISIS: 52h
The Hysteresis parameter adds to or subtracts from the finger threshold depending on whether the sensor is currently active or
inactive. If the sensor is off, the difference count must overcome the ‘finger threshold + hysteresis’. If the sensor is on, the difference
count must go below the ‘finger threshold – hysteresis’. It is used to add debouncing and “stickiness” to the finger detection algorithm.
This parameter is common for all sensors.
Possible values are 0 to 255. However, the setting must be lower than the finger threshold parameter setting. Recommended value
for hysteresis is 15 percent of finger threshold.
1/2 Button
7654321
0
Access: FD
RW: 00
RW: 0
Bit Name
CS_CLK[1:0]
Sns_Ar
Bit
Name
Description
6:5
CS_CLK[1:0]
These bits selects the CapSense clock.
3
Sns_Ar
This bit is used to enable or disable sensor auto reset.
0
1
Disable Sensor auto reset
Enable Sensor auto reset
CS_CLK[1:0]
Frequency of Operation
00
IMO
01
IMO/2
10
IMO/4
11
IMO/8
1/2 Button
7654321
0
Access: FD
RW:0A
Bit Name
HYS[7:0]
Bit
Name
Description
7:0
HYS [7:0]
These bits are used to set the hysteresis value.
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