Let's start by thinking about the size of the ROM. I would prefer two separate ROMS, one for the tens and one for the ones.
Each of them needs all the bits of the result. These are 6 bits, so the Address Bit Width is 6.
The outputs of the ROMs drive directly the segments of the LEDs. We need to control each of the segments. These are 7 segments per LED, so the Data Bit Width is 7.
Now we need to put the right data into the ROM to configure it. I did it like this:
- Put the ROMs behind a 6-bit counter, because this is the fastest way to check all 64 values. You can copy the ROMs and LEDs later into the adder circuit.
- Reset the simulation, which will set the counter to 0.
- Open the "Hex Editor" by right clicking a ROM and selecting "Edit Contents…". Note that you need to close it, if you want to edit the other ROM.
- Edit the value at cell 00 until the correct digit is shown on the accompanied LED. You need some understanding how binary values and hex values are connected. You might need to jot down a table.
- Repeat this with the other ROM.
- Click the clock generator (with the poke tool, not the edit tool) so that the counter counts up by 1.
- Repeat both editing steps for the next numbers, until you have all ROM values for the digits from 0 to 9 (on the ones ROM) and from 0 to 6 (for the tens ROM).
- Now copy manually the respective values in all ROM cells. The ROM for the ones will get the sequence 0-1-2-3-4-5-6-7-8-9-0-...-9-0-1-2-3. The ROM for the tens will get 0-0-0-0-0-0-0-0-0-0-1-1-...-1-2-2-...-5-6-6-6-6.
If you rather like to use a single ROM, you will need 14 data bits. The method to fill the ROM is still the same.