Si1000/1/2/3/4/5
7.6. Comparator0 and Comparator1 Analog Multiplexers
Comparator0 and Comparator1 on Si1000/1/2/3/4/5 devices have analog input multiplexers to connect
Port I/O pins and internal signals the comparator inputs; CP0+/CP0- are the positive and negative input
multiplexers for Comparator0 and CP1+/CP1- are the positive and negative input multiplexers for
Comparator1.
The comparator input multiplexers directly support capacitive touch switches. When the Capacitive Touch
Sense Compare input is selected on the positive or negative multiplexer, any Port I/O pin connected to the
other multiplexer can be directly connected to a capacitive touch switch with no additional external compo-
nents. The Capacitive Touch Sense Compare provides the appropriate reference level for detecting when
the capacitive touch switches have charged or discharged through the on-chip Rsense resistor. The Com-
parator outputs can be routed to Timer2 or Timer3 for capturing sense capacitor’s charge and discharge
time. See Section “27. Timers” on page 330 for details. See Application Note AN338 for details on Capaci-
tive Touch Switch sensing.
Any of the following may be selected as comparator inputs: Port I/O pins, Capacitive Touch Sense Com-
pare, VDD_MCU Supply Voltage, Regulated Digital Supply Voltage (Output of VREG0) or ground. The
Comparator’s supply voltage divided by 2 is also available as an input; the resistors used to divide the volt-
age only draw current when this setting is selected. The Comparator input multiplexers are configured
using the CPT0MX and CPT1MX registers described in SFR Definition 7.5 and SFR Definition 7.6.
CPTnMX
P0.1
P0.3
P0.5
P0.7
P0.0
P0.2
P0.4
P0.6
CPnOUT
Rsense
CPnOUT
Rsense
P1.5
P1.7
P2.1
P2.3
P2.5
P1.6
P2.0
P2.2
P2.4
P2.6
Only enabled when
Capacitive Touch
Sense Compare is
selected on CPn+
Input MUX.
Only enabled when
Capacitive Touch
Sense Compare is
selected on CPn-
Input MUX.
Capacitive
Capacitive
CPn-
Input
MUX
CPn+
Input
MUX
VDD_MCU
VDD_MCU
R
CPnOUT
R
VDD_MCU CPnOUT
Touch
Sense
Touch
Sense
R
R
Compare
Compare
+
-
(1/3 or 2/3) x VDD_MCU
(1/3 or 2/3) x VDD_MCU
R
R
VDD_MCU
R
VDD_MCU
R
GND
½ x VDD_MCU
Digital Supply
½ x VDD_MCU
VBAT
R
R
VDD_MCU
GND
Figure 7.4. CPn Multiplexer Block Diagram
Important Note About Comparator Input Configuration: Port pins selected as comparator inputs should
be configured as analog inputs, and should be skipped by the Digital Crossbar. To configure a Port pin for
analog input, set to 0 the corresponding bit in register PnMDIN and disable the digital driver (PnMDOUT =
0 and Port Latch = 1). To force the Crossbar to skip a Port pin, set to 1 the corresponding bit in register
PnSKIP. See Section “21. Port Input/Output” on page 207 for more Port I/O configuration details.
106
Rev. 1.0
SILICON [ SILICON ]
