User Manual
P A G E 20
E a s y P I C v 8 M a n u a l
C O N N E C T I V I T Y
INPUT/OUTPUT section
I/O pins of any MCU are internally grouped as PORTs. The same grouping concept is
kept throughout the development board as well, off ering a clean and organized user
interface.
There are fi ve PORTs (1) on the EasyPIC v8 development board, labeled from PORTA to
PORTE. Depending on the pin-count of the MCU, not all PORTs will be used. However,
the development board supports the highest pin-count MCUs in DIP package type (40
pins). The PORTs are located at the lower right side of the board, each containing a
set of eight buttons, eight LEDs, an eight-pole DIP switch, and a single 2x5 pin header
with the standard 2.54mm pitch. The PORTs are labeled according to the MCU PORT
they are routed to.
PORT buttons
PORT buttons (2) can be used to apply an arbitrary logic state to the pins of the MCU.
These buttons are small tactile SPST buttons that work in combination with a DIP
switch (SW5), labeled as BUTTONs PRESS LEVEL. This DIP switch is located in the
BOARD SETUP section.
BUTTONs PRESS LEVEL switch
This eight-pole, tri-state DIP switch allows the button to apply a LOW logic level to an
MCU pin when pressed (connecting it to the GND), or to apply a HIGH logic level when
pressed (connecting it to the power rail). It can also be used to completely disconnect
the button, preventing accidental button presses. To limit the pin current and prevent
the excessive inrush of currents when a button is pressed, a protective 220Ω resistor is
used, connected in series with the switch. Each position of the BUTTONs PRESS LEVEL
switch (3) is used to determine the applied logic level of a button press for the entire
PORT. As a result, only fi ve poles of this DIP switch are used, allowing control of all
fi ve groups of buttons (unused poles are marked with the NC label - Not Connected).
BUTTONs PRESS LEVEL:
UP position: a button press applies HIGH logic level to the corresponding PORT pins
MID position: a button is completely disconnected
DOWN position: a button applies LOW logic level to the corresponding PORT pins
UP-PULL-DOWN switch
Besides buttons, each of the fi ve PORTs has an eight-pole DIP switch associated with
it. It is labeled as UP-PULL-DOWN (4) and it is used to enable a pull-up or pull-down
resistor for the specifi c pin or to leave the pin in a fl oating state:
UP-PULL-DOWN:
UP position: connects a 4.7kΩ resistor between the MCU power rail and the pin (the
pin is pulled up)
MID position: Disables both pull-up and pull-down resistor connections from the
pin (the pin is in the fl oating state)
DOWN position: Connects the 4.7kΩ resistor between the GND and pin associated with
the DIP switch position (the pin is pulled down)
PORT LEDs
Each PORT contains a group of eight LEDs (5) used to provide a visual indication
of the logic state of the specifi c pin. The maximum current through a single LED is
limited with the 4.7kΩ resistor. Each LED is connected to a PORT pin and it is labeled
according to the name of the connected pin (RA0 to RE7). LEDs on each PORT should
be disconnected when not used. Having a LED on a communication line or an A/D
converter input might alter expected results since LED represents an additional
electrical load. There is a ten-pole DIP switch (SW6) (6) located in the BOARD SETUP
section. Five poles of this DIP switch, labeled as PORT LEDs are used to enable or
disable LEDs on each PORT: