User Manual

E a s y P I C v 8 M a n u a l
P A G E 19
VCAP and VCC
For some of the PIC MCU devices, the manufacturer (Microchip) suggests using
additional bypass capacitors for improved stability. These MCUs use internal
voltage regulators since their cores operate at diff erent (lower) voltages than their
peripherals. For some applications, it may be necessary to use bypass capacitors,
in order to ensure better noise immunity. This applies to DIP40 (2) and DIP28 (3)
sockets. However, the EasyPIC v8 development board off ers a choice, since each pin
on these low pin-count MCUs can be very valuable.
Next to the DIP40 MCU socket, there is a two-pole DIP switch (4) used to specify
whether the VCAP/RA4 and VCAP/RA5 pins will be used as GPIOs on this MCU socket,
or connected to the onboard bypass capacitors:
RA4/RA5 (DIP40)
VCAP (up): connects the RA4 and RA5 pins to the onboard capacitors
GPIO (down): allows the RA4 and RA5 pins to be used as GPIO lines
Next to the DIP28 MCU socket, there is another two-pole DIP switch (5) used to
specify whether the VCAP/RA4 and VCAP/RA5 pins will be used as GPIOs on this MCU
socket, or connected to the onboard bypass capacitors:
RA4/RA5 (DIP28)
VCAP (up): connects the RA4 and RA5 pins to the onboard capacitors
GPIO (down): allows the RA4 and RA5 pins to be used as GPIO lines
Next to the DIP28 MCU socket, there is an additional DIP switch labeled as SW20 (6).
This switch is used if the MCU installed in the DIP28 socket requires an analog voltage
supply (VCC) to be connected:
SW20:
UP position: redirects the RA5 pin to be used either as the VCAP or as the GPIO
(depending on the RA4/RA5 DIP switch settings)
DOWN position: Connects the RA5 pin to the power supply rail (for MCUs that
require VCC on this pin)
Crystal oscillator
Most of PIC MCU devices can use an external quartz-crystal oscillator. There are two
sockets for installing the crystal oscillator, depending on which MCU socket will be
used:
Crystal oscillator socket OSC1 is routed to DIP40, DIP28, DIP18A, and DIP18B MCU sockets (7)
Crystal oscillator socket OSC2 is routed to DIP20, DIP14, and DIP8 MCU sockets (8)
10F MCUs do not use external oscillators. Consequently, none of the crystal oscillator
socket pins are routed to the 10F MCU DIP socket.
Above the DIP28 MCU socket, there is a DIP switch (9) used to specify whether the
OSC1/RA6 and OSC1/RA7 pins will be used as GPIOs on the corresponding MCU
sockets, or connected to the OSC1 crystal oscillator socket:
RA6, RA7 (OSC1)
UP position: allows the RA6 and RA7 pins to be used as GPIO lines
DOWN position: connects the RA6 and RA7 pins to the crystal oscillator socket OSC1
Below the two DIP8 MCU sockets, there is a DIP switch (10) used to specify whether
the OSC2/RA4 and OSC2/RA5 pins will be used as GPIOs on the corresponding MCU
sockets, or connected to the OSC2 crystal oscillator socket:
RA4, RA5 (OSC2)
UP position: allows the RA4 and RA5 pins to be used as GPIO lines
DOWN position: connects the RA4 and RA5 pins to the crystal oscillator socket OSC2
C O N N E C T I V I T Y
When using MCU devices that require the analog voltage supply pin to be
connected to the power source (such as PIC18F2331 or PIC18F2431), the
SW20 switch must be in the DOWN position.
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N O T E 10F MCU families do not use an external crystal oscillator. Consequently, none
of the crystal oscillator socket pins are routed to the 10F MCU DIP socket.