Screen Shot of Working Simulation
I noticed when I was working with logisim the D-flip-flops (DFF) I created using NAND gates always started out in an error state. It took a full clock cycle for them to correct this then they functioned properly until the next reset. I have a trigger using a DFF that must start low so I needed to build it to make sure it starts low. Most of my NAND chips are on order but I did find one left over from a project I did a few years back.
Initial Power On DFF from NAND
As you can see from the picture the /Q line is active on power on. The white wire is the D input and the brown wire is the Clock. After clocking in a HIGH:
DFF from NAND HIGH state
It works! I always get excited when I see LEDs light up when they are supposed to light up. This proved that the DFF does start in the LOW state and does work.
I have started working on the LED matrix, specifically on how to defuse the LEDs and make them into nice looking squares... but more on that in the next post.