Datasheet

Programming PIC Microcontrollers in BASIC - mikroElektronika
and as such is not suitable for the supply of microcontroller. To avoid the pulsating,
the electrolytic capacitor of high capacitance (e.g. 470 mF) is placed at the rectifier
output.
● If PIC microcontroller supervises devices that pull a lot of energy, they may provoke
enough malfunctioning on the supply lines to cause the microcontroller start behaving
somewhat strangely. Even seven-segmented LED display may well induce tension
drops (the worst scenario is when all the digits are 8, when LED display needs the
most power), if the source itself is not capable to procure enough current (e.g. 9V
battery).
● Some PIC microcontrollers feature multi-functional I/O pins, for example
PIC16C62x family (PIC16C620, 621 and 622). Controllers of this family are
provided with analog comparators on port A. After putting those chips to work, port
A is set to analog mode, which brings about the unexpected behavior of the pin
functions on the port. Upon reset, any PIC with analog inputs will show itself in
analog mode (if the same pins are used as digital lines they need to be set to digital
mode). One possible source of troubles is that the fourth pin of port A exhibits
singular behavior when it is used as output, because the pin has open collectors output
instead of usual bipolar state. This implies that clearing this pin will nevertheless set
it to low level, while setting the pin will let it float somewhere in between, instead of
setting it to high level. To make the pin behave as expected, the pull-up resistor was
placed between RA4 and 5V. Its magnitude is between 4.7K and 10K, depending on
the current necessary for the input. In this way, the pin functions as any other input
pin (all pins are output after reset).
More problems are to be expected if you plan to be seriously working with PIC. Sometimes
the thing seems like it is going to work, but it just won’t, regardless of the effort. Just
remember that there is always more than one way to solve the problem, and that a different
approach may bring solution.
PIC, PIC, PICmicro, and MPLAB are registered and protected trademarks of the Microchip
Technology Inc. USA. Microchip logo and name are the registered tokens of the Microchip
Technology. mikroBasic is a registered trade mark of mikroElektronika. All other tokens mentioned
in the book are the property of the companies to which they belong.
http://www.mikroelektronika.co.yu/english/product/books/picbasicbook/01.htm (10 sur 11)05/11/2004 02:10:07