PIC18F85K22-I/PT Microchip Technology, PIC18F85K22-I/PT Datasheet - Page 390

• Manufacturer Part Number: PIC18F85K22-I/PT
• Description: IC, 8BIT MCU, PIC18F, 64MHZ, TQFP-80
• Manufacturer: Microchip Technology
• Series: PIC® XLP™ 18Fr

Specifications of PIC18F85K22-I/PT

• Controller Family/series: PIC18
• No. Of I/o's: 69
• Eeprom Memory Size: 1KB
• Ram Memory Size: 2KB
• Cpu Speed: 64MHz
• No. Of Timers: 8
• Core Size: 8 Bit
• Program Memory Size: 32KB
• Core Processor: PIC
• Speed: 64MHz
• Connectivity: EBI/EMI, I²C, LIN, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LVD, POR, PWM, WDT
• Number Of I /o: 69
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 2K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 24x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 80-TQFP
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

PIC18F87K22 FAMILY
27.2.5
The CTMU sets its interrupt flag (PIR3<3>) whenever
the current source is enabled, then disabled. An inter-
rupt is generated only if the corresponding interrupt
enable bit (PIE3<3>) is also set. If edge sequencing is
not enabled (i.e., Edge 1 must occur before Edge 2), it
is necessary to monitor the edge status bits and
determine which edge occurred last and caused the
interrupt.
27.3
The following sequence is a general guideline used to
initialize the CTMU module:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10. Disable the module by clearing the CTMUEN bit
11. Clear the Edge Status bits, EDG2STAT and
12. Enable both edge inputs by setting the EDGEN
13. Enable the module by setting the CTMUEN bit.
DS39960D-page 390
Select the current source range using the
IRNGx bits (CTMUICON<1:0>).
Adjust the current source trim using the ITRIMx
bits (CTMUICON<7:2>).
Configure the edge input sources for Edge 1 and
Edge 2 by setting the EDG1SEL and EDG2SEL
bits (CTMUCONL<3:2> and <6:5>, respectively).
Configure the input polarities for the edge inputs
using the EDG2POL and EDG1POL bits
(CTMUCONL<7,4>).
The default configuration is for negative edge
polarity (high-to-low transitions).
Enable edge sequencing using the EDGSEQEN
bit (CTMUCONH<2>).
By default, edge sequencing is disabled.
Select the operating mode (Measurement or
Time Delay) with the TGEN bit.
The
Measurement.
Configure the module to automatically trigger
an A/D conversion when the second edge
event has occurred, using the CTTRIG bit
(CTMUCONH<0>).
The conversion trigger is disabled by default.
Discharge the connected circuit by setting the
IDISSEN bit (CTMUCONH<1>).
After waiting a sufficient time for the circuit to
discharge, clear IDISSEN.
(CTMUCONH<7>).
EDG1STAT (CTMUCONL<1:0>).
bit (CTMUCONH<3>).
CTMU Module Initialization
default
INTERRUPTS
mode
is
Time/Capacitance
Depending on the type of measurement or pulse
generation being performed, one or more additional
modules may also need to be initialized and configured
with the CTMU module:
• Edge Source Generation: In addition to the
• Capacitance or Time Measurement: The CTMU
• Pulse Generation: When generating system clock
27.4
The CTMU requires calibration for precise measure-
ments of capacitance and time, as well as for accurate
time delay. If the application only requires measurement
of a relative change in capacitance or time, calibration is
usually not necessary. An example of a less precise
application is a capacitive touch switch, in which the
touch circuit has a baseline capacitance and the added
capacitance of the human body changes the overall
capacitance of a circuit.
If actual capacitance or time measurement is required,
two hardware calibrations must take place:
• The current source needs calibration to set it to a
• The circuit being measured needs calibration to
27.4.1
The current source on board the CTMU module has a
range of ±60% nominal for each of three current
ranges. For precise measurements, it is possible to
measure and adjust this current source by placing a
high-precision resistor, R
channel. An example circuit is shown in
To measure the current source:
1.
2.
3.
4.
5.
6.
external edge input pins, CCPx Special Event
Triggers can be used as edge sources for the
CTMU.
module uses the A/D Converter to measure the
voltage across a capacitor that is connected to one
of the analog input channels.
independent, output pulses, the CTMU module
uses Comparator 2 and the associated
comparator voltage reference.
precise current.
measure or nullify any capacitance other than that
to be measured.
Initialize the A/D Converter.
Initialize the CTMU.
Enable the current source by setting EDG1STAT
(CTMUCONL<0>).
Issue the settling time delay.
Perform the A/D conversion.
Calculate the current source current using
I = V / R
resistance and V is measured by performing an
A/D conversion.
Calibrating the CTMU Module
CURRENT SOURCE CALIBRATION
CAL
, where R
 2009-2011 Microchip Technology Inc.
CAL
CAL
, onto an unused analog
is a high-precision
Figure
27-2.