Colour Selection

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.

The character display works the same way as the graph. Its memory locations range from $F000 to $F7CF and have 25 lines of 80 characters (80x25). The complication here is the navigation between rows. It is not a matter of just increment the high bite – meaning more code and more working hours. Fortunately, we have ROM routines to help us to navigate, get and set the characters. Just like calling a function.

To know more about the ROM routines, access the 6502 simulator notes and take a look at "ROM Routines."

I tried to put as many comments in the code that I could. Also, that was my first time using the stack (instructions pha and pla) that saved my code! The stack is a handy area to save data when you need to free registers to do something and then restore that data.

I'm proud of myself finishing this code. I know that is room for improvement, but I can see my progress using assembly. See you in the next post.

Comments

Project Stage 2

Photo by SpaceX on Unsplash Hey! Were you curious about the results of profiling AWK ? Me too! Quick recap, what is profiling, and how to do it? Profiling is a technique to map the time execution of each part of the application. We can add instrumentation to the executable, or use interruption sampling to generate that map. Here, I’ll use both. Click here for more details on profiling . For the instrumentation, we have to tell the compiler to add the tools needed to collect the execution data. So, I’ve changed the “makefile” file, CFLAGS variable with “-g -Og -pg” and ran the make command. Then, I just ran the awk the same way I did to benchmark it. Here is the command line: ./awk 'BEGIN {FS = "<|:|=";} {if ($8 == "DDD>") a ++;} END {print "count: " a;}' bmark-data.txt This awk version, instrumented, generates a file gmon.out, which contains all execution data. This is the raw material to create a profile report using gp

Assembly?

Photo by Jonas Svidras on Unsplash Last week on my SPO course, I had my first experience writing Assembly code. I won’t lie; it was struggling. For me, Assembly is like the Latin of the codding languages and “carpe diem” wasn’t my first lesson. Hexadecimal, binary and a list of instructions is a must know to guarantee survival. Our instructor introduced us to the 6502 processor: it is an old school chip that was used in many home solutions such as PCs and video games. Internally, it has three general-purpose registers, three special-purpose registers, memory and input and output ports. Fortunately, there are emulators on the internet that helps us to focus on the development, hiding the electronic part from us. http://6502.cdot.systems/ Using the emulator, our first task was to copy, paste and execute a piece of code to change the colour of every pixel in the display matrix. That was easy! The result was a yellow screen. Then we were asked to introduce so

Two-digit Numeric Display

Photo by Nick Hillier on Unsplash Hi! I'm continuing my blog about my SPO classes. After a brief introduction in Assembly, we are good to hit Lab3. Our instructor kindly let us choose one project out of five. And of course, we decided to go with the easiest! We had to do a two-digit numeric display where the numbers are incremented or decremented by pressing plus and minus key in the keyboard. Soon the challenges were reviled as we dive into how to code it. Should we treat every digit separated or together? How to print them into the display? After a moment of reflection, we decided to handle the digits independently to facilitate the printing display. Also, we had to add a bit-map representation of the numbers because the 6502 chip doesn’t know any font. In this post, I’ll show you the code with the logic to increment and decrement without displaying anything. You can monitor the address $13 and $14 to make sure that it is working. Let me expla

Rodrigo

Search This Blog