Questions about PIC16F677

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- 6th January 2008, 11:06
fnovau

Questions about PIC16F677

I begin a project with PIC16F677 and I should like to ask the experts of
this forum some questions.Here are some details of my application:
1-Pins RA0, RA1 and RA3 are free. If I use internal pull up resistor for
RA3/MCLR can I let this pin floating and save diode protection during programming?
2- Pic will be feed through a batery and should be sleeping as much time
as possible. I will use RA2 as an analog input and I pretend to use IOC
for waking up the system when input RA2 changes but
Which is the minimum input volt change for starting an IOC action?
Is it a risky situation to use IOC for reliable operation of the system considering input signal RA3 is generated by an op-amp with high gain?
3- For generating previous description I imagine I have to setup these registers:
TRISA, ANSEL, IOCA, INTCON,ADCON0, ADCON1 and for disable comparators
CM1CON0 and CM1CON1=0 but Do I forget anything else?
Thank you in advanced for any help
-Francesc
- 6th January 2008, 21:58
Darrel Taylor

Quote:

Originally Posted by fnovau

I will use RA2 as an analog input and I pretend to use IOC
for waking up the system when input RA2 changes but
Which is the minimum input volt change for starting an IOC action?

When the PIN is in Analog mode, a digital "Read" always returns 0.
Therefore, an IOC will never happen.
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- 14th January 2008, 20:26
fnovau

Questions about PIC16F677

[QUOTE=fnovau;48669]I begin a project with PIC16F677 and I should like to ask the experts of
this forum some questions.Here are some details of my application:
1-Pins RA0, RA1 and RA3 are free. If I use internal pull up resistor for
RA3/MCLR can I let this pin floating and save diode protection during programming?

Does anybody can answer or give me any hint about question 1?
- 15th January 2008, 06:26
paul borgmeier

>>1-Pins RA0, RA1 and RA3 are free. If I use internal pull up resistor for
RA3/MCLR can I let this pin floating and save diode protection during programming?

Yes - if you are using RA3 as MCLR (MCLRE = 1), the internal pull-up will keep it high so you do not need to tie this pin to anything, which saves the diode between the pin and the VDD rail. However, if you are in a noisy environment, you might want to consider using the internal MCLR pull-up (MCLRE = 0) or add the diode and a 1.0K resistor in line to the rail.