Datasheet

2011-2012 Microchip Technology Inc. Preliminary DS61168E-page 215
PIC32MX1XX/2XX
24.0 CHARGE TIME
MEASUREMENT UNIT (CTMU)
The Charge Time Measurement Unit (CTMU) is a flex-
ible analog module that has a configurable current
source with a digital configuration circuit built around it.
The CTMU can be used for differential time measure-
ment between pulse sources and can be used for gen-
erating an asynchronous pulse. By working with other
on-chip analog modules, the CTMU can be used for
high resolution time measurement, measure capaci-
tance, 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
16-edge input trigger sources
Selection of edge or level-sensitive inputs
Polarity control for each edge source
Control of edge sequence
Control of response to edges
High precision time measurement
Time delay of external or internal signal asynchro-
nous to system clock
Integrated temperature sensing diode
Control of current source during auto-sampling
Four current source ranges
Time measurement resolution of one nanosecond
A block diagram of the CTMU is shown in Figure 24-1.
FIGURE 24-1: CTMU BLOCK DIAGRAM
Note 1: This data sheet summarizes the fea-
tures of the PIC32MX1XX/2XX family of
devices. It is not intended to be a
comprehensive reference source. To
complement the information in this data
sheet, refer to Section 37. “Charge
Time Measurement Unit (CTMU)”
(DS61167) in the “PIC32 Family
Reference Manual”, which is available
from the Microchip web site
(www.microchip.com).
2: Some registers and associated bits
described in this section may not be
available on all devices. Refer to
Section 4.0 “Memory Organization” in
this data sheet for device-specific register
and bit information.
CTED1
CTED13
Current Source
Edge
Control
Logic
CTMUCON1 or CTMUCON2
Pulse
Generator
CTMUI
Comparator 2
Timer1
OC1
Current
Control
ITRIM<5:0>
IRNG<1:0>
CTMUICON
CTMU
Control
Logic
EDG1STAT
EDG2STAT
ADC
CTPLS
IC1-IC3
CMP1-CMP3
C2INB
CDelay
CTMUT
Temperature
Sensor
Current Control Selection TGEN EDG1STAT, EDG2STAT
CTMUT 0 EDG1STAT = EDG2STAT
CTMUI 0 EDG1STAT EDG2STAT
CTMUP 1 EDG1STAT EDG2STAT
No Connect 1 EDG1STAT = EDG2STAT
Trigger
TGEN
CTMUP
External capacitor
for pulse generation
(To ADC S&H capacitor)
(To ADC)
PBCLK