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

PIC24F04KA201 FAMILY
2.6 External Oscillator Pins
Many microcontrollers have options for at least two
oscillators: a high-frequency primary oscillator and a
low-frequency secondary oscillator (refer to
Section 8.0 “Oscillator Configuration” for details).
The oscillator circuit should be placed on the same
side of the board as the device. Place the oscillator
circuit close to the respective oscillator pins with no
more than 0.5 inch (12 mm) between the circuit
components and the pins. The load capacitors should
be placed next to the oscillator itself, on the same side
of the board.
Use a grounded copper pour around the oscillator
circuit to isolate it from surrounding circuits. The
grounded copper pour should be routed directly to the
MCU ground. Do not run any signal traces or power
traces inside the ground pour. Also, if using a
two-sided board, avoid any traces on the other side of
the board where the crystal is placed. A suggested
layout is shown in Figure 2-4.
For additional information and design guidance on
oscillator circuits, please refer to these Microchip
Application Notes, available at the corporate web site
(www.microchip.com):
• AN826, “Crystal Oscillator Basics and Crystal
Selection for rfPIC™ and PICmicro^® Devices”
• AN849, “Basic PICmicro^® Oscillator Design”
• AN943, “Practical PICmicro^® Oscillator Analysis
and Design”
• AN949, “Making Your Oscillator Work”
FIGURE 2-4:
SUGGESTED PLACEMENT
OF THE OSCILLATOR
CIRCUIT
Main Oscillator
13
Guard Ring
14
15
Guard Trace
16
Secondary
17
Oscillator
18
19
20
2.7 Configuration of Analog and
Digital Pins During ICSP
Operations
If the MPLAB ICD 2, ICD 3 or REAL ICE emulator is
selected as a debugger, it automatically initializes all of
the A/D input pins (ANx) as “digital” pins by setting all
bits in the AD1PCFGL register.
The bits in this register that correspond to the A/D pins
that are initialized by the MPLAB ICD 2, ICD 3 or REAL
ICE emulator must not be cleared by the user
application firmware; otherwise, communication errors
will result between the debugger and the device.
If your application needs to use certain A/D pins as
analog input pins during the debug session, the user
application must clear the corresponding bits in the
AD1PCFGL register during initialization of the ADC
module.
When the MPLAB ICD 2, ICD 3 or REAL ICE emulator
is used as a programmer, the user application firmware
must correctly configure the AD1PCFGL register.
Automatic initialization of this register is only done
during debugger operation. Failure to correctly
configure the register(s) will result in all A/D pins being
recognized as analog input pins, resulting in the port
value being read as a logic ‘0’, which may affect user
application functionality.
2.8 Unused I/Os
Unused I/O pins should be configured as outputs and
driven to a logic low state. Alternatively, connect a 1 kΩ
to 10 kΩ resistor to VSS on unused pins and drive the
output to logic low.
DS39937B-page 18
Preliminary
© 2009 Microchip Technology Inc.