Project 4 has two files, Mult.asm and Fill.asm.
Mult
Mult.asm is multiplication. You have to do R0 * R1 and put that in R2. It is important to note to get the value at R0 you would do
@0
D = M //stores R0 at D
The memory address is not R0 but 0. Remember that you have to put an infinite loop at the end to say that the program is finished. It shouldn’t be too difficult.
Fill
Fill is supposed to fill the screen with black when a key is pressed. A block of 16 pixels is consider a word. @SCREEN is the position of the first word of the screen. If a pixel holds a value of 1 this will make the pixel black. Otherwise it is white.If you assign a word to have a value of -1, which is 1111111111111111 in binary, it will turn the first 16 pixels black.
@SCREEN
M = -1 // this is referencing the first word
(END)
@END
0;JMP
This will make the first 16 pixels black and is a good test script to make sure you that you have the write steps to run your program.
The screen has 32 words in each row and has a total of 256 rows meaning that there are 8192 words in total. The easiest way to go at this is assigning each of these words with a value of -1. Start with @SCREEN
To tell if you need to fill the screen, you have to tell if key is pressed. This is as simple as getting the value at the keyboard address which is @24576. If the value doesn’t equal zero at that memory position then a key is currently pressed.
@24576 // memory address of the keyboard.
D = M
D has the value of the key being pressed. It is 0 if no key is pressed.
All of this is given in the book. I wanted to make it easier for people to get what it is saying.
Testing and Compiling
To compile your *.asm file, run assembler.bat or .sh and then click load source file on the very left. If you press the blue arrows it will compile it slowly so to get it done quickly press the while paper with numbers on it(directly left of the equals sign). The save icon next to the open file should turn blue and you can click on it and save the .hack file.
Next run CPUEmulator.bat or .sh. For Mult you can click on the script button, the same as in HardwareSimulator, and run the test file and you got your result. For Fill you will have to press the open file on the very left and open Fill.hack in the /Fill folder. Next on the right, set animations to no animations. Then set view to screen. Click on the keyboard button on the bottom and then you can press any key, other than ctrl and some modifier buttons, and see the results. An error of At line 32XXX: Can't continue past last line usually means that you forgot to end the program with an infinite loop.
It is important to note that sometimes the assembler might bug out with overwriting so you might want to delete the .hack file and then save