Cant figure out the CPU.HDL

[ammarr]

i read the 5th chapter and and re read chapter 2 and 4 to try to understand the CPU.HDL but i still cant figure it out

i always get error in the 3rd line
set instruction %B1110110000010000, // D=A

Comparison failure at line 3

i am trying to do it similar to figure 5.9,

and i understand C-instruction and A-instruction from figures 4.3 ,4.4 & 4.5

but i still cant figure out how to handle a C-instruction and A-instruction in the cpu.hdl

any hint will be great
thanks

[ybakos]

What is the value of the most significant bit of an A instruction and a C instruction?

[ammarr]

Thanks  ybakos

i just realized that i was counting from right to left instead from left to right

i mean for the C instruction
i started the top most as 0 until and ended j3 = 15

now i fixed this, so my top most is 15

this is how i start my code
Mux16(a=instruction,b=Backin,sel=instruction[15],out=AorD);

and it worked but now am facing another problem

comparison failure at line 8 // D=D-A

[cadet1620]

ammarr wrote

... but now am facing another problem

comparison failure at line 8 // D=D-A

Hardware debugging involves collecting clues about the error and reasoning out plausible causes for it. There is a lot more information at the failure point than just the line number.

The CPU is executing a D=D-A instruction, so you need to look at the previous output line to see what the values of the D and A registers were, and the current line to see what the new, presumably wrong, value of D is and figure out what went wrong with the computation. The "Compare" line shows the expected value of D. Note that the A register shows up on addressM.

It's also possible that the new D value is correct and something else like the jump hardware went wrong.

It's sometimes easier to look at the .cmp and .out files in a text editor.

--Mark

[ammarr]

hi

i think am mostly done

am just stuck with the Load of the PC ,still cant get the condition right

am trying to find the combination of j3,j2,j1,ng,zr

still struggling ......

[cadet1620]

A hint for the jump logic is to create a pos status flag from zr and ng. Then it's easy to test if any of the status flags and their corresponding instruction bits are set.

--Mark

[ammarr]

Thanks alot

finally got it working

i spent nearly a week with the CPU with 4-5 hours daily,

but it always feels great to get things to work.

in the beginning i didn't understand what you meant by

cadet1620 wrote

 create a pos status flag from zr and ng. --Mark

i thought you meant Nand, where i get a 1 in all cases of ng  and zr

but then i realized that you meant a positive output of the ALU, that is a positive outM and not a positive state

so i used Xor with Not to get the po


any way to get the condition of the load of the PC i used

1 Xor
1 Not
14 And
1 Or8Way


is there a simpler way to optimize it.

Thanks for the course and great support......

[cadet1620]

Answered by e-mail.

--Mark