i need help with this antique microprocessor project

[celocider]

The project i am currently working on is a digital clock using the user's port of that trainer which is configured with the 8255 ic.

I was able to make the hardware work and configure the hardware to use Port A0 to A3 and Port C0 to C5 of 8255 as bidirectional ports to run my circuit.. i'll post the circuit later after i edit it with eagle software.

Just to give you an idea of how circuit uses the ic, I'm currently doing a digital clock hardware project for microprocessors which is purposed to be interfaced with an ANALAB z8 Emulator User's port which is equivalent to an 8255 ic. The power supplied to the emulator is seperated with the +5 V supplied to my circuit.

My circuit uses six common anode 7 segment display to show time with an active low bcd-to-7segment decoder that are limited with 470K ohms resistors. The bcd inputs A,B,C and D are connected to the ports A0, A1, A2, and A3 respectively of the 8255. The six 7 segment displays have been alloted one BC547B NPN transistor each with their collectors connected to +VCC and their bases connected to 330 ohm resistors. The Bases of the transistors are then connected to Port C0,C1,C2,C3,C4,C5 of the 8255. Assuming nothing more is to be done, my problem now is initializing 8255 in my main program to use handshaking of signals.

I have included my program for the chip so you may check on it. Please tell me what i'm doing wrong...

 

[kchriste]

The project i am currently working on is a digital clock using the user's port of that trainer which is configured with the 8255 ic

Your diagram shows that you aren't using the 8255 and are instead connecting the 7 segment driver circuit directly to your ANALAB z8 Emulator User's port..... That's what your schematic shows, unless you mean that the 8255 is on the ANALAB z8 Emulator PCB?

active low bcd-to-7segment decoder that are limited with 470K ohms resistors.

I assume you mean 470hm: and NOT 470Khm:
Lastly, please don't post stuff in M$Word format. Use plain text format for code.

 

[celocider]

Your diagram shows that you aren't using the 8255 and are instead connecting the 7 segment driver circuit directly to your ANALAB z8 Emulator User's port..... That's what your schematic shows, unless you mean that the 8255 is on the ANALAB z8 Emulator PCB?

Yes, the 8255 ic is on the analab z8 emulator. Is the 470k ohm resistor not recommended for the circuit? i'm currently using 470k ohms because i'm assuming the pin out interface can out a voltage of 4 - 5 volts as logic 1.. are my assumptions incorrect? i dont own a trainer so i can't test it and were on semestral break so i can't go to school to check on the equipment. I'm just relying on testing the output of the circuit by tapping voltage on the circuit.

 

[kchriste]

Is the 470k ohm resistor not recommended for the circuit?

The LEDs would be too dim for you to see. Use 470hm:

 

[celocider]

i'm currently enrolling for school so it would take me about two weeks to reply for the results. pm you guys later.

 

[celocider]

ok so i'm back with this project... also tried to change the 470k with 470 ohms.. still i'm not getting any display.. can someone check on my program that i posted earlier.. thanks