16F628 & In-Circuit Programming?

[Len]

Hi group,

I would like to utilize in-circuit programming with a 16F628 for a project. Pins RB6 & RB7 which are CLK and DATA for the programming functions will have to be shared as they are also used in the non-programming application. My question is:

Are RB6 and RB7 automatically set as INPUTS when -MCLR is raised to 12V for programming? (because they are used as OUTPUTS) in the non-programming application.

Also, there is a picture in the PIC16F62X spec sheet on Pp. 106 showing resistors in series with the "normal connections" and wonder why they are there, and what values are appropriate.

Thanks for any suggestions.

[NavMicroSystems]

Sharing the ICSP clock and data pins should not be a problem as long as they are used as outputs in your "normal application"

It might be a problem if they are used as inputs in your "normal application" as this means they are connected to the output of some other device which might be pulling the PIC pin high (or low) while you are trying to program it.

I think the resistors in series are just for current limiting and are not really necessary.
If you want to install them their values should be low in relation to the pullups on RB6/RB7 (if you use any)

rgds