Texas Instruments MSP430x1xx - Manual (Page 273)

Comparator_A Control Registers
14-7
Comparator_A
CARSEL, bit6: The internal reference V
CAREF
, selected by CAREF bits,
is applied to the +terminal or –terminal.
0: Reference is selected to the +terminal (CAEX = 0) or
–terminal (CAEX = 1)
1: Reference is selected to the –terminal (CAEX = 0) or
+terminal (CAEX = 1)
CAEX, bit7: The inputs of the comparator are exchanged. This is
used to measure or compensate for the offset of the
comparator.
14.3.2 Comparator_A, Control Register CACTL2
The control register CACTL2 is shown and described below.
P2CA1 P2CA0
CACTL
2.7
7
rw-(0)
CACTL
2.6
rw-(0)
CACTL
2.5
rw-(0) rw-(0) rw-(0) rw-(0)
CAF
rw-(0)
CAOUT
0
r-(0)
CACTL2
05Ah
CACTL
2.4
CAOUT, bit0: The comparator output. Writing to this bit, for example
when writing a new register value, has no affect or
negative impact.
CAF, bit1: The comparator output filter is bypassed (CAF=0) or
switched into the output path (CAF=1).
P2CA0, bit2: Pin to CA0
0: The external, pin signal is not connected to the
Comparator_A
1: The external, pin signal is connected to the
Comparator_A
P2CA1, bit3: Pin to CA1
0: The external, pin signal is not connected to the
Comparator_A
1: The external, pin signal is connected to the
Comparator_A
Bits 4–7: See device data sheet for implementation.
14.3.3 Comparator_A, Port Disable Register CAPD
Typically, the comparator input and output functions are multiplexed with
digital I/O port pins to save pin count on a device. Also, slope A/D applications
often utilize multiple digital I/O ports (for charging and discharging) to provide
multiple channels of slope A/D conversion. In these multichannel applications,
a useful feature of the digital I/O pins is the ability to disable the input buffer.
Typically, all channels except the one being converted are disabled, providing
a high-impedance input and avoiding current consumption caused by through-
put current. (See section 14.4.1)
The typical digital I/O ports on MSP430 do not have the ability to disable the
input buffer. However, on devices with the Comparator_A, the capability has
been added and is controlled with the CAPD.x bits.