18F2550 and Blink Led

[towlerg]

The config you have seems fine but unless you want to use the watchdog turn WDT off and you can turb VREGEN off as you're not using USB. One question though, if you aren't using USB, why not use a device similar to 2550 but with additional features and more memory eg 18F25K22?

[n0yox]

I was not aware of the 18F25K22. I should have asked for advice before I made the change. Sometimes selecting a new device can be very confusing. I will look at the data sheet for the 18F25K22 , do you have any other suggestions for a 16f648a substitute with more memory. I don’t really need the extra I/O’s just more code space.
Thank you very much!

[Dave]

If you are looking for a direct replacement I would suggest the 16F1847. Faster and twice the memory.

[n0yox]

Thank you, I will make an order on Monday. I should have asked before I started this project.
I have tried to use the pic comparison page with some luck http://www.microchip.com/maps/microcontroller.aspx
Melabs once had a very simple chart that compared many of the most common controller however they deleted that page.

I have one more question about the 18f2550 can anyone tell me how to turn on the weak pullups on the top 4 of PORTB “4-7”.

[n0yox]

Is this close?
INTCON2 = %00000000 ' makes all of portb have WPU ? INTCON2<7> 'page 116
TRISB = %00001111 'B. 0:3 are now outputs WPU is now off?

[tumbleweed]

To enable the pullups on PORTB just clear the RPBU bit in INTCON2 using INTCON2.7 = 0. It's an all or nothing thing on that chip... you can't set them individually.

TRISB = %00001111 'B. 0:3 are now outputs WPU is now off?

The comment doesn't match the setting, but to set PORTB 7:4 to inputs and the others (3:0) to outputs you'd use
TRISB = %11110000

The WPU is only enabled when the pin is set to input mode (TRIS bit = 1). It's disabled when the pin is an output (TRIS bit = 0)

[n0yox]

What I was attempting to say with that comment was that by using TRISB = %00001111 after the line containing INTCON2.7 = 0 you would set the bottom 4 bits to outputs causing those 4 bits to no longer have WPU , Maybe I have this backward and it should be TRISB = %11110000 Is this also wrong? As it turns out I need all 8 ports to have WPU’s so I will not be using that line. However for future use I would like to know the correct usage?
Thank you so much!