Old and beyond help ?

[mackrackit]

1. Can I use RA6 and RA7 as outputs if there is a xtal connected across them ( do not know what the DC characteristics of a xtal are)

No , you will have to use the internal OSC.

2. How the devil do I program the 16F887 so that those two pins are available as outputs. I understand that I have to set up the configuration word (register 1) so that bits 2 -0 are 100 which should set the two pins as available for I/O (subject to item 1 ((above)) But what is the syntax for doing this ? I see no rference in the Picbasic manual (or anywhere else) to this. I have looked at examples but cannot figure it out from that. Any advice on this would be appreciated
Cheers

@__config _CONFIG1, _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_OFF & _LVP_OFF & _CP_OFF

So you did not like the shift registers?

[DavidFMarks]

Hi,
I have set the oscillator to internat but since the crystal is already mounted on the 44 pin board I did not really want to remove it ! .. and yes I dis like the shift register idea but need more time to get my ancient brain around it and to obtain the chips ( Meanwhile Christmas lights are going up all round me !)

[mackrackit]

My board did not come with an external OSC mounted, I assumed yours did not also.

I thought you were asking if the chip was running off the XT could the pins be used as an output.

Is it Monday or something?

[DavidFMarks]

Sorry you are right, there is no crystal (it's my age) I still haven't figured out where the terms in your config expression come from. They are clearly assembler terms of some kind

[mackrackit]

Are you using PM or MPASAM for the assembler?
If you are using MPASAM, ( my choice) goto program files,microchip,mpasamsuite and find the *.inc file for your chip. At or near the end of the file all of the different fuse settings are listed.

http://www.picbasic.co.uk/forum/showthread.php?t=543
Goes into more detail. Pay close attention to Melanie and Mister_E.

If you are still unclear let us know.

[mackrackit]

(it's my age)

How old are you???

Look at my avatar. That is really me

[DavidFMarks]

Many thanks for that, Had a quick look at the link ..looks just the thing I wanted, Bit late to study now, bedtime & just got in from g daughters school musical. Age ? put it this way, Faraday hadn't satrted shaving when I got into this game and I aint going to seeing the good old three score years and ten again so its good to be helped by all you patient youngsters ! Thanks again !

[DavidFMarks]

Hi again,
Got the porta I/O proble sorted insofar as i can now switch on any of the a port bits and light an led. Or so I thought, I wrote a program which switched on each bit of the port in turn held it with a pause 500 command and then switched it off and so on. When writing te Christmas star program I wrote simple code tp switch on all of the bits of PortA (they are each connected through Darlingtons to the - line of one of 16 arms (the other 8 are driven from portc by identical code (other than the port id). Now what happens is that only pins 4 6 and 8 remain high (leds lit). I have now written a separate little piece of code to test it. If I switch each pin on in turn pausing between each one (but not switching them off ) then led 0 switches on and after the specified delay it switches off and the next one comes on. only when I get to pins 4 6 and 8 do they stay switched on. Another curiousity which may be a clue is that when I compile and program the pickit2 comes on with a lower Vdd(about 3.8 and I have to turn it up again. I have also removed the darlingtons so there are only leds an port A but it has made no difference. If anyone can spot whatever my latest stupid mistake is I would be very grateful. BTW the reason I could'nt originally use pins 6 an7 was that [I] had my knickers in a twist thinking I was programming with MPASm when in fact I was using the default !!