PRELIMINARY
CY8C20111, CY8C20121
Document Number: 001-53516 Rev. **
Page 13 of 34
7.7 CS_NOISE_TH
Noise Threshold Register
CS_NOISE_TH: 4Eh
This register sets the noise threshold value. For individual sensors, count values above this threshold do not update the baseline.
This count is relative to baseline. This parameter is common for all sensors.
The range is 3 to 255 and it should satisfy the equation NT < Min (Finger Threshold – Hysteresis – 5). Recommended value is 40%
of finger threshold.
7.8 CS_BL_UPD_TH
Baseline Update Threshold Register
CS_BL_UPD_TH: 4Fh
When the new raw count value is above the current baseline and the difference is below the noise threshold, the difference between
the current baseline and the raw count is accumulated into a “bucket.” When the bucket fills, the baseline increments and the bucket
is emptied. This parameter sets the threshold that the bucket must reach for the baseline to increment. In other words, lower value
provides faster baseline update rate and vice versa. This parameter is common for all sensors.
The range is 0 to 255.
7.9 CS_SETL_TIME
Settling Time Register
CS_SETL_TIME: 50h
(Writable only in Setup mode)
The settling time parameter controls the duration of the capacitance-to-voltage conversion phase. The parameter setting controls a
software delay that allows the voltage on the integrating capacitor to stabilize. This parameter is common for all sensors.
This register should be set before setting finger threshold (0x66, 0x67) and IDAC setting (0x70, 0x71) registers.
The range is 2 to 255.
1/2 Button
7
6
5
4
3
2
1
0
Access: FD
RW:28
Bit Name
NT[7:0]
Bit
Name
Description
7:0
NT [7:0]
These bits are used to set the noise threshold value.
1/2 Button
7654321
0
Access: FD
RW:64
Bit Name
BLUT[7:0]
Bit
Name
Description
7:0
BLUT [7:0]
These bits set the threshold that the bucket must reach for baseline to increment.
1/2 Button
7654321
0
Access: FD
RW:A0
Bit Name
STLNG_TM[7:0]
Bit
Name
Description
7:0
STLNG_TM [7:0]
These bits are used to set the settling time value.
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