PIC18F87J90 Datasheet, PDF (309/450 Pages) Microchip Technology – 64/80-Pin, High-Performance Microcontrollers with LCD Driver and nanoWatt Technology

PIC18F87J90 FAMILY
24.0 CHARGE TIME
MEASUREMENT UNIT (CTMU)
The Charge Time Measurement Unit (CTMU) is a
flexible analog module that provides accurate differen-
tial time measurement between pulse sources, as well
as asynchronous pulse generation. By working with
other on-chip analog modules, the CTMU can be used
to precisely measure time, measure capacitance,
measure relative changes in capacitance or generate
output pulses with a specific time delay. The CTMU is
ideal for interfacing with capacitive-based sensors.
The module includes the following key features:
• Up to 13 channels available for capacitive or time
measurement input
• On-chip precision current source
• Four-edge input trigger sources
• Polarity control for each edge source
FIGURE 24-1:
CTMU BLOCK DIAGRAM
• Control of edge sequence
• Control of response to edges
• Time measurement resolution of 1 nanosecond
• High-precision time measurement
• Time delay of external or internal signal
asynchronous to the system clock
• Accurate current source suitable for capacitive
measurement
The CTMU works in conjunction with the A/D Converter
to provide up to 13 channels for time or charge
measurement, depending on the specific device and the
number of A/D channels available. When configured for
time delay, the CTMU is connected to one of the analog
comparators. The level-sensitive input edge sources
can be selected from four sources: two external inputs or
the CCP1/CCP2 Special Event Triggers.
Figure 24-1 provides a block diagram of the CTMU.
CTEDG1
CTEDG2
CCP2
CCP1
EDGEN
EDGSEQEN
EDG1SELx
EDG1POL
EDG2SELx
EDG2POL
EDG1STAT
EDG2STAT
CTMUCON
CTMUICON
ITRIM<5:0>
IRNG<1:0>
Current Source
TGEN
IDISSEN
CTTRIG
Edge
Control
Logic
Current
Control
CTMU
Control
Logic
A/D Converter Comparator 2
Input
Pulse
Generator
Comparator 2 Output
A/D Trigger
CTPLS
 2010 Microchip Technology Inc.
DS39933D-page 309