In our Assembly Language subject, we are asked to do a simple up down counter (0-9). The circuit comprises of 5 switches. The first switch triggers the increment procedure, while the 2nd switch will trigger the decrement command. The 3rd switch is programmed to have a set function, that means if you want to start the counter at a specific number, you need to press this button. It's almost the same with the 1st switch, though the 3rd switch does not perform an continuous increment. Pressing the 4th switch will pause the current command. Lastly, the reset switch will make the counter roll back to 0.
We're allowed to use the 7447 IC (decoder) in this activity, thus making the source code shorter. I just connected the 1st 4 pins of the output side of the parallel cable to the legs of the IC which is responsible accepting the binary value to be displayed in the 7-segment. A external source was also used for the parallel cable's current value can't trigger the IC. Don't forget to make a delay procedure in your program!