Rodrigo

Photo by  Marvin Meyer  on  Unsplash Continuing the Lab 4, we are going to develop the option 2, data input form. The goal is to prompt the user to enter its name, address, city, province and postal code. Also, letting the user use up, down, left, and right arrows to navigate throughout the fields. After finishing the data input, a summary is presented at the end. Using the ROM routines, wasn’t too hard to allow users to type data into the character display. Then, I decided to make the filed names with the same width, 14 characters, limiting the input to 40 characters. So, the user is not allowed to type in the first 14 and after 54 characters. When the user presses enter at the last field, the summary is shown. I could display the fixed message, but I couldn’t copy the inserted data. I’m still working on that, and I’ll update this post as soon I figure it out. It is frustrating for me to spend days in basic problems that could be solved quickly using other languages. Assembly

Photo by Scott Webb  on  Unsplash Today I'll talk about Lab 4. We had to pick two tasks out of four and develop the solution using my least favour language: assembly. Our group chose the options 2 (data input form) and 4 (screen colour selector) thinking that would be the easiest ones. The other options were adding calculator and hexdump. This post will talk about the colour selector, and my next will be the input form. The colour selector project was quite easy to do relatively. There are only 16 colours available (0 to F in hex). We have to list them in the text area and allow the selection using the cursor (up and down). Once the colour is selected, we have to paint the graph area. The graph area we did before. Basically, we have to store the colour code for every pixel in the display using the memory location between $0200 and $05FF. In the last post, we deal with up and down keys to change the numeric display. However, we never dealt with character display before.

Photo by  Nick Hillier  on  Unsplash In this post, I’ll continue the two-digit numeric display. If you miss it, click here and check it out . To finish this project, we just need to show the numbers in the matrix-pixel (the black-box in the 6502 emulator ). To kickstart, our instructor gave us one example of how to display graphs, which was a lot helpful. The first thing that I’ve noticed was the bitmap table at the bottom. So, I mimic it and made ten tables like that to represent each number (zero to nine). So far, so good! Then I grabbed the logic to display one digit, and then my nightmares just started. How to place two graphs (one for each digit)? How to switch from one number to another? How to reuse code? Where is my coffee?! To emulate some if-elseif-else statements, I used jmp (jump). They are all over the place! However, the 6502 limits the jump range from -127 to 128. That means moving the code-blocks to satisfy all jumps limit. For example, the “m