Port b on velleman 8048

Kits Microcontroller Programmer - Experimenting Project
1

Hello all!

I try to make a clock on 8048 kit, with the enclosed PIC 16f627. Since I need 4 pins for output (i use a bcd to 7 segment decoder to drive the led display) and 4 bits for multiplexing, i try to use all pins of the port b. Unfortunately, portb,6 and portb,7 seem to be always on - the display looks weird (a randomly sparkling 8) at the corresponding digits, although the application runs fine on simulator and also i can get on those digits something like a response when pressing the adjusting buttons (some segments look a little more bright). I look at the schematic of the project and i see that there are some resistors pulling up those pins (from the programing part of the board), but even after i remove those resistors, i don’t get any improvements.

So, i want to know if any of you run into the same problem trying to use all pins of the port b, and if so, what is the remedy. I think i should try a stand-alone version of the project, but i am afraid that the pcb is to difficult to manufacture.

Any sugestion/help wold be higly appreciated. Thanks!

2

Careful, RB6 and RB7 are also used for programming clock and data.
Probably, it will work fine stand alone.

3

Yes, you have to use 2 other port pins to make up your port.

These pics use PB6+7 for the serial communications and programming on a development board.

Temporarily use 2 others until those pins aren’t used for programming or debugging. YOU ONLY NEED TO LEARN THIS LESSON ONCE - IT APPLIES TO MANY PICS.

4

Hi, sorry to hijack this topic but because my problem is similar (I assume) to this one I will ask here ^^

Well I was trying something on my PIC and because I was lazy I configure PORTB as output for all pins, and now when I try to reprogram well it doesn’t work (picprog tells me it doesn’t match). Is there any way to force a full erase of the chip or something ?

Cheers