Matrix user forums

Hi Guys,
I have a few working projects and want to start building some proto boards for them and am wondering what I need to watch out for? My chip it the 16F877A one question is that my EB-006 has the switch at XTAL selected. I am assuming that this is for the external crystal that is on my EB-006? If I am using an standard LCD on PortB do I have to use an external crystal or can I use the chip oscillator?

I found this note:

3: RA4 is an open collector I/O pin. When
used as an output, a pull-up resistor is
required

I could not find what value the resistor should be?
And does it mean the pin is ready to go as input without the resistor? But to use it as an output the resistor should be installed to pin RA4 and +5 volt?

For low buck projects should opto isolators be utilized?

Thanks for the help!!

Werner

Hello Werner,

If I am using an standard LCD on PortB do I have to use an external crystal or can I use the chip oscillator?

Internal oscillator will work fine. Though do not use if you need highly accurate timing.

I could not find what value the resistor should be?
And does it mean the pin is ready to go as input without the resistor? But to use it as an output the resistor should be installed to pin RA4 and +5 volt?

4.7K or 10K pullup between RA4 and +5V should do the job fine and is only needed if you want to be able to output a logic 1 on that pin.

For low buck projects should opto isolators be utilized?

It really depends on what you are connecting your circuitry to. I rarely use opto's in my designs but there are times when they come in very handy for protection.