DSPIC33FJ12MC201TESS datasheet(17/304 Pages) MICROCHIP

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DS70265E-page 17

dsPIC33FJ12MC201/202

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.

Alternately, refer to the AC/DC characteristics and tim-

ing 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 Debugger

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 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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