DSPIC33FJMC202ESS datasheet(15/330 Pages) MICROCHIP

15 / 330 page

DS70283K-page 15

dsPIC33FJ32MC202/204 and dsPIC33FJ16MC304

2.5

ICSP Pins

The PGECx and PGEDx pins are used for In-Circuit

Serial Programming (ICSP) and debugging purposes.

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 3 or MPLAB REAL ICE™ in-circuit emu-

lator.

For more information on MPLAB ICD 3 or MPLAB

REAL

ICE™

in-circuit

emulator

connection

requirements, refer to the following documents that are

available on the Microchip web site.

• “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™ In-Circuit Emulator”

(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 8.0 “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

Guard Ring

Guard Trace

Secondary

Oscillator

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