This project demonstrates how BitMagic can be used to generate data, in this case a set of Sin tables.
The sin tables are created to move a 8x8 sprite around the screen.
The tables will be 256 entries long, so make it easier to index into.
For the X axis these will have to be between 0 and 320 - 8. We minus 8 so the sprite doesn't move off the screen. As the value range is above 255, these values will need to be 16bit.
To speed up reading the X axis values, these 16bit numbers will be split into a low and high value table.
The Y axis is simpler, values between 0 and 240 - 8 are required, so a 8bit table can be used.
The sin tables are generated at the end of the program.
There are two functions GetYData() and GetXData() which generate the 256 entry long values. The output of which is then passed into a library function BM.Bytes, BM.LowBytes or BM.HighBytes which creates a data block depending on the function.
Before these blocks are defined there is a .align $100 to make sure that the start aligns to a memory block so when we use lda ydata, x there is no cycle penalty for going across a memory bank.
After the data there are 4 variables defined using .var. This keyword allocates the space for the data type and initialises the value by storing it inside the file from the segment. .var cannot be used inside segments that do not produce a file, .padvar should be used instead but without the initial value.)
The benefit of defined a variable and its type (either using .var, .constvar or .padvar) is that these values are visible in the variables section within VSCode while debugging. They appear under the Locals entry near the bottom.
