PIC24FJ128GA310-I Datasheet, PDF (324/406 Pages) Microchip Technology – 64/80/100-Pin, General Purpose, 16-Bit Flash Microcontrollers with LCD Controller and nanoWatt XLP Technology

PIC24FJ128GA310 FAMILY
FIGURE 27-1:
TYPICAL CONNECTIONS AND INTERNAL CONFIGURATION FOR
CAPACITANCE MEASUREMENT
PIC24F Device
Timer1
CTMU
EDG1 _{Current Source}
EDG2
Output Pulse
A/D Converter
ANx
ANY
CAPP
RPR
27.2 Measuring Time
Time measurements on the pulse width can be similarly
performed using the A/D module’s internal capacitor
(CAD) and a precision resistor for current calibration.
Figure 27-2 displays the external connections used for
time measurements, and how the CTMU and A/D
modules are related in this application. This example
also shows both edge events coming from the external
CTEDG pins, but other configurations using internal
edge sources are possible.
27.3 Pulse Generation and Delay
The CTMU module can also generate an output pulse
with edges that are not synchronous with the device’s
system clock. More specifically, it can generate a pulse
with a programmable delay from an edge event input to
the module.
When the module is configured for pulse generation
delay by setting the TGEN bit (CTMUCON1<12>), the
internal current source is connected to the B input of
Comparator 2. A capacitor (CDELAY) is connected to
the Comparator 2 pin, C2INB, and the comparator
voltage reference, CVREF, is connected to C2INA.
CVREF is then configured for a specific trip point. The
module begins to charge CDELAY when an edge event
is detected. When CDELAY charges above the CVREF
trip point, a pulse is output on CTPLS. The length of the
pulse delay is determined by the value of CDELAY and
the CVREF trip point.
Figure 27-3 illustrates the external connections for
pulse generation, as well as the relationship of the
different analog modules required. While CTED1 is
shown as the input pulse source, other options are
available. A detailed discussion on pulse generation
with the CTMU module is provided in the “PIC24F
Family Reference Manual”.
DS39996F-page 324
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