Fill.asm

[George]

Can someone please tell me how you draw a rectangle for Fill.asm? All I have is one line

[cadet1620]

George wrote

Can someone please tell me how you draw a rectangle for Fill.asm? All I have is one line

Section 4.2.5 describes how the screen works; read it carefully.  Memory address 16384 is the first word of screen memory.  It sounds like you are only writing to 16384 so you only get a 16 pixel long line in the upper left corner of the screen.  You need to write to all the words in the screen memory to make the screen all black.

--Mark

[George]

Thank you so much.

[linuxford]

cadet1620 wrote

Section 4.2.5 describes how the screen works; read it carefully.  Memory address 16384 is the first word of screen memory.  It sounds like you are only writing to 16384 so you only get a 16 pixel long line in the upper left corner of the screen.  You need to write to all the words in the screen memory to make the screen all black.

--Mark

I believe I am on the right track. My thinking is that each memory address holds a 16-bit word and if I can flip all the bits to 1 for the 16-bit word then it will display black for that section. I then can loop through and do that to all the words (8K~8192). It seems to be sort of working but I am having trouble setting the MSB of the 16-bit word to 1.

Could you please give me a hint?

[cadet1620]

linuxford wrote

... It seems to be sort of working but I am having trouble setting the MSB of the 16-bit word to 1.

Could you please give me a hint?

What is the signed-integer value of a word that is all 1 bits?

--Mark

[linuxford]

cadet1620 wrote

linuxford wrote

... It seems to be sort of working but I am having trouble setting the MSB of the 16-bit word to 1.

Could you please give me a hint?

What is the signed-integer value of a word that is all 1 bits?

--Mark

2^16 is 65536. 65536/2 is 32768, so signed 16-bit integer represented values range from -32768..0..32767.

If I use the
@-1
it will give me the a 16-bit pattern of all 1's - 1111 1111 1111 1111
However, if I do that, the CPU don't like that. It seems as soon as I make the MSB 1, that it is not an A-instruction but is instead a C-instruction perhaps.

[cadet1620]

Correct.  You can't set -1 with an A-Instruction.  Look at the C-Instruction comp table in 6.2.2.

--Mark

[linuxford]

cadet1620 wrote

Correct.  You can't set -1 with an A-Instruction.  Look at the C-Instruction comp table in 6.2.2.

--Mark

Haha... got it. I'll take a crack at it this evening after I get off from work. Thanks Mark