8-Pin PIC pin availability on Multiprogrammer ports

[Pughie]

I am having a little difficulty understanding the detail in the datasheet regarding which 8-Pin PIC pins are available on the Multiprogrammer I/O ports. I am experimenting with a PIC12F675 and, if I understand it correctly, only GP0, GP1 and GP2 are made available to the user on Ports RB7, RB6 and RA0 respectively. Is this the case please? My circuit uses a 10MHz Crystal therefore I/O ports GP4 and GP5 are connected to this but is the remaining I/O GP3 available anywhere on the Multiprogrammer pins?

[DavidA]

Hi Pughie,

As far as I know (and microcontrollers are not my forte) the GP3 is the MCLR which cant be used as an output, but may be used as an input if the 'Master Clear Enable' is set to Internal in the config settings.

[Benj]

Hello,

GP3 is connected to the reset switch so you can use the reset switch as an input to the RE3 pin if you setup the configuration correctly.

[Pughie]

Many thanks to both Benj and DavidA for your help on this one. As it happens, my hope was to use GP3 as an Input and I now understand how to set this up in the config settings. It appears that I was correct in my original assumption that GP0, GP1 and GP2 are made available to the user on Ports RB7, RB6 and RA0 respectively on the Multiprogrammer, since neither of you disagreed with this. Perhaps I understood the data sheet on the Multiprogrammer better than I first thought

[Benj]

Hello,

GP0, GP1 and GP2 are made available to the user on Ports RB7, RB6 and RA0

Yes sorry about that. You are correct with your connections.

[Pughie]

Many thanks again, Ben. Your E-blocks are superb to design projects with, I have several modules here including two PIC Multiprogrammers. I needed two because I have designed some equipment which needed to have a serial link between the two separate ends on which I used two of your E-block RS232 boards. I am pleased to say that I have managed to get it all working perfectly including the utilisation of a rotary encoder at one end. My current project which uses the PIC12F675 is a huge backward step from the two code intensive, serial-linked PIC16F877A's in the previous one. With the backing of your good selves and my hero, the late John Becker, I am having a whale of a time programming PICs at the moment. Many thanks again to you all. John

[Pughie]

Dear Benj. Sorry to come back to you on this but could I trouble you to check one small detail in your reply to me on 5th March please. You wrote :-
'GP3 is connected to the reset switch so you can use the reset switch as an input to the RE3 pin'.
Did you mean to say RA3 and not RE3? The Multiprogrammer shares the 14 pin socket with the 8 pin one and I notice that the PIC pinout diagrams on page 11 of the data sheet for EB0-006 shows RA3 connected to the MCLR pin 4 of the 14-pin PIC Micro diagram, which is also the MCLR pin in the adjacent 8-pin PIC Micro diagram. If you meant to write 'RA3' my understanding is that Port RA3 can be used as an input to GP3 on the 8-pin PIC Micro socket of the Multiprogrammer. The way I intend to use it is to tie this pin 4 (via Port RA3) to the 5V supply using a 4k7 resistor and short the pin to ground via an external pushbutton. I just want to be sure that my understanding is correct before I cause harm to my Multiprogrammer board. Many thanks.

[Benj]

Hello,

Yes I did mean RA3, not sure where that E came from . you could use the reset switch on the multiprogrammer as your external input or as you say you could wire in your own.

[Pughie]

Many thanks for your swift and helpful response, Ben.