C8051F970-A-GM Datasheet, PDF (130/454 Pages) Silicon Laboratories – Low Power Capacitive Sensing MCU with up to 32 kB of Flash

C8051F97x
18. Capacitive Sense (CS0)
The Capacitive Sense subsystem uses a capacitance-to-digital circuit to determine the capacitance on a port pin.
The module can take measurements from different port pins using the module’s analog multiplexer. The module is
enabled only when the CS0INT bit (CS0CN) is set to 1. Otherwise the module is in a low-power shutdown state.
The module can be configured to take measurements on one port pin or a group of port pins, using auto-scan. A
selectable gain circuit allows the designer to adjust the maximum allowable capacitance. An accumulator is also
included, which can be configured to average multiple conversions on an input channel. Interrupts can be
generated when CS0 completes a conversion or when the measured value crosses a threshold defined in
CS0THH:L.
Important Note: The CS0 module and the ADC0 module cannot both be enabled at the same time. Even if one
module is enabled and not running, the other module must not be enabled.
CS0PM
CS0CN
CS0CF
CS0SS CS0SE
Auto-Scan
Logic
Pin Monitor
Port I/O and
Peripherals
000
Start
001
Conversion
010
011
100
101
110
111
CS0BUSY (W)
Timer 0 Overflow
Timer 2 Overflow
Timer 1 Overflow
Timer 3 Overflow
Reserved
Initiated continuously
Initiated continuously
when auto-scan
enabled
From
AM0 Pad
Selector
...
1x-8x
Capacitance to ^{12, 13, 14, or 16 bits}
Digital Converter
22-Bit Accumulator
CS0DH:L
CS0WOI
CS0EOS
Wake up
event logic
Wake-up
signal
CS0MD1
Greater Than
Compare Logic
CS0MD2
CS0MD3
CS0THH:L
Figure 18.1. CS0 Block Diagram
CS0CMPF
CS0CMPEN
CS0POL
CS0WOI
130
Rev 1.0