DSPIC33EP64GS708 datasheet(19/484 Pages) MICROCHIP

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DS70005258C-page 19

dsPIC33EPXXXGS70X/80X FAMILY

2.5

ICSP Pins

The PGECx and PGEDx pins are used for 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 con-

nector 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 Voltage Input High

(VIH) and Voltage 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® PICkit™ 3, MPLAB ICD 3, or MPLAB

REAL ICE™.

For more information on MPLAB ICD 2, MPLAB ICD 3

and REAL ICE connection requirements, refer to the

following documents that are available on the

Microchip website.

• “Using MPLAB® ICD 3 In-Circuit Debugger”

(poster) (DS51765)

• “Development Tools Design Advisory” (DS51764)

• “MPLAB® REAL ICE™ In-Circuit Emulator User’s

Guide for MPLAB X IDE” (DS50002085)

• “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. For details, see 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

Guard Ring

Guard Trace

Oscillator Pins

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