70291E Datasheet, PDF (23/436 Pages) Microchip Technology – High-Performance, 16-bit Digital Signal Controllers

dsPIC33FJ32MC302/304, dsPIC33FJ64MCX02/X04 AND dsPIC33FJ128MCX02/X04
2.5 ICSP Pins
The PGECx and PGEDx pins are used for In-Circuit
Serial Programming™ (ICSP™) and debugging pur-
poses. It is recommended to keep the trace length
between the ICSP connector and the ICSP pins on the
device as short as possible. If the ICSP connector is
expected to experience an ESD event, a series resistor
is recommended, with the value in the range of a few
tens of Ohms, not to exceed 100 Ohms.
Pull-up resistors, series diodes, and capacitors on the
PGECx and PGEDx pins are not recommended as they
will interfere with the programmer/debugger communi-
cations to the device. If such discrete components are
an application requirement, they should be removed
from the circuit during programming and debugging.
Alternatively, refer to the AC/DC characteristics and
timing requirements information in the respective
device Flash programming specification for information
on capacitive loading limits and pin input voltage high
(VIH) and input low (VIL) requirements.
Ensure that the “Communication Channel Select” (i.e.,
PGECx/PGEDx pins) programmed into the device
matches the physical connections for the ICSP to
MPLAB^® ICD 2, MPLAB^® ICD 3 or MPLAB^® REAL
ICE™.
For more information on ICD 2, ICD 3 and REAL ICE
connection requirements, refer to the following
documents that are available on the Microchip web
site.
• “MPLAB^® ICD 2 In-Circuit Debugger User’s
Guide” DS51331
• “Using MPLAB^® ICD 2” (poster) DS51265
• “MPLAB^® ICD 2 Design Advisory” DS51566
• “Using MPLAB^® ICD 3” (poster) DS51765
• “MPLAB^® ICD 3 Design Advisory” DS51764
• “MPLAB^® REAL ICE™ In-Circuit Emulator User’s
Guide” DS51616
• “Using MPLAB^® REAL ICE™” (poster) DS51749
2.6 External Oscillator Pins
Many DSCs have options for at least two oscillators: a
high-frequency primary oscillator and a low-frequency
secondary oscillator (refer to Section 9.0 “Oscillator
Configuration” for details).
The oscillator circuit should be placed on the same
side of the board as the device. Also, place the
oscillator circuit close to the respective oscillator pins,
not exceeding one-half inch (12 mm) distance
between them. 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 them 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 2-3.
FIGURE 2-3:
SUGGESTED PLACEMENT
OF THE OSCILLATOR
CIRCUIT
Main Oscillator
13
Guard Ring
14
15
Guard Trace
16
Secondary
17
Oscillator
18
19
20
© 2011 Microchip Technology Inc.
DS70291E-page 23