Texas Instruments MSP430x4xx - Manual (Page 326)

Comparator_A Operation
17-6 Comparator_A
17.2.5 Comparator_A, Port Disable Register CAPD
The comparator input and output functions are multiplexed with the associated
I/O port pins, which are digital CMOS gates. When analog signals are applied
to digital CMOS gates, parasitic current can flow from V
CC
to GND. This
parasitic current occurs if the input voltage is near the transition level of the
gate. Disabling the port pin buffer eliminates the parasitic current flow and
therefore reduces overall current consumption.
The CAPDx bits, when set, disable the corresponding P1 input buffer as shown
in Figure 17−3. When current consumption is critical, any P1 pin connected to
analog signals should be disabled with their associated CAPDx bit.
Figure 17−3. Transfer Characteristic and Power Dissipation in a CMOS Inverter/Buffer
V
CC
V
SS
I
CC V
O
VI
0 V
CC
VI
V
CC
I
CC
CAPD.x = 1
17.2.6 Comparator_A Interrupts
One interrupt flag and one interrupt vector are associated with the
Comparator_A as shown in Figure 17−4. The interrupt flag CAIFG is set on
either the rising or falling edge of the comparator output, selected by the
CAIES bit. If both the CAIE and the GIE bits are set, then the CAIFG flag
generates an interrupt request. The CAIFG flag is automatically reset when
the interrupt request is serviced or may be reset with software.
Figure 17−4. Comparator_A Interrupt System
D Q
IRQ, Interrupt Service Requested
Reset
VCC
POR
SET_CAIFG
IRACC, Interrupt Request Accepted
CAIE
CAIES
0
1