PIC24F04KA201 Datasheet, PDF (162/224 Pages) Microchip Technology – 14/20-Pin General Purpose, 16-Bit Flash Microcontrollers with nanoWatt XLP™ Technology

PIC24F04KA201 FAMILY
22.2 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 22-2 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.
22.3 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 (CTMUCON<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 22-3 shows the external connections for pulse
generation, as well as the relationship of the different
analog modules required. While CTEDG1 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”.
FIGURE 22-2:
TYPICAL CONNECTIONS AND INTERNAL CONFIGURATION FOR TIME
MEASUREMENT
CTEDG1
CTEDG2
PIC24F Device
CTMU
EDG1 _{Current Source}
EDG2
Output Pulse
A/D Converter
ANx
CAD
RPR
FIGURE 22-3:
TYPICAL CONNECTIONS AND INTERNAL CONFIGURATION FOR PULSE
DELAY GENERATION
CTEDG1
PIC24F Device
CTMU
EDG1
CTPLS
C2INB
Current Source
Comparator
-
C2
CDELAY
CVREF
DS39937B-page 160
Preliminary
© 2009 Microchip Technology Inc.