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--- notes:comporg:spring2025:projects:dapx [2025/03/02 23:52] – [Preserving our Registers] cgrant9
+++ notes:comporg:spring2025:projects:dapx [2025/03/09 15:44] (current) – [Masking] Made asm code format consistent tkastne1
@@ Line 10: / Line 10: @@
 =====Preserving our Registers=====
-For our debug to work with any given code we need to preserve everything that we may be using; part of this is to save the contents o our registers.\\
+For our debug to work with any given code we need to preserve everything that we may be using; part of this is to save the contents of our registers.\\
 To do this we can set up a local stack to save the contents of our register while we use them with the instructions:
@@ Line 16: / Line 16: @@
 PUSH BP
 MOV  BP, SP
+</code>
+Once we set up a local stack, we can push all of our registers onto this new stack, while still having access to the previous stack with some manipulations.\\
+Once you have done everything you need to, you need to restore your registers and stack.\\
+For the registers, simply pop them off the stack in reverse order, i.e if you pushed 0-13, you will pop 13-0.
+The stack can be just as simple as that, or more difficult depending on your approach. The simpler approach is to do the reverse of creating a local stack, that is:
+<code>
+MOV  SP, BP
+POP  BP
 </code>
 =====Preserving our Textures=====
+Along with preserving your register you need to preserve your texture and region, this should be done after preserving at least one of your registers, as we need to use a register to get the data to preserve.\\
+Once we have preserved our registers, simply use the 'IN' instruction to get information from the GPU port like this:
+<code>
+IN   R0, GPU_SelectedTexture
+PUSH R0
+IN   R0, GPU_SelectedRegion
+PUSH R0
+</code>
+And just like our registers, we need to pop them in reverse order to restore them when we're done:
+<code>
+POP  R0
+OUT  GPU_SelectedRegion, R0
+POP  R0
+OUT  GPU_SelectedTexture, R0
+</code>
 =====bitwise operations=====
 ====OR====
 ====AND====
+The AND op code will do an and comparison of two values
+<code>
+mov  R0,  0x00F00000
+mov  R1,  0x12689649
+and  R0,  R1
+</code>
+This code will leave us with 0x00600000 because every other value was put into and with a zero.
 ====NOT====
 ====NAND====
@@ Line 29: / Line 60: @@
 ====SHIFT====
-===Shift Right====
 ===Shift Left===
+A shift left can be done with the op code SHL
+<code>
+mov  R0,  0x00F00000
+mov  R1,  4
+shl  R0,  R1
+</code>
+This code will give R0 the value 0x0F000000 because the original value was left-shifted by 4 bits.
+===Shift Right====
+There isn't an op code provided by Vircon32 for right shifts, so we must shift left by a negative value.
+<code>
+mov  R0,  0x00F00000
+mov  R1,  -4
+shl  R0,  R1
+</code>
+This code will give R0 the value 0x000F0000 because we shifted the original value to the left by -4 bits.
 =====pseudocode=====
@@ Line 63: / Line 108: @@
 ASCII code for 0 --> decimal 48, hexadecimal 0x30
 ASCII code for x --> 120
-ASCII code for [ --> 92
+ASCII code for [ --> 91
 ASCII code for ] --> 93
 ASCII code for : --> 58
@@ Line 81: / Line 126: @@
 ====Masking====
+We need to get a nibble on it's own, to do this we can use a bit mask
+A mask only allows certain bit positions to be either 1 or 0, and forces everything else to be 0
+This is done with the **and** operator
+In order to get the most significant nibble we would want a mask of 0xF0000000 (0b11110000000000000000000000000000)
+<code>
+mov   R1,   0xF0000000  ; Creating the mask
+and   R1,   R0          ; R0 is the original value
+</code>
+To get the second most significant nibble, instead of creating a new mask by hand, we can shift the old mask over by a nibble ever time we loop
+We should have a register keep track of our loop count
+<code>
+mov   R2,   R3          ; R3 is the loop count
+imul  R2,   -4          ; Left shift bits per nibble
+mov   R1,   0xF0000000  ; Creating the mask
+shl   R1,   R2
+and   R1,   R0          ; R0 is the original value
+</code>
 ====Shifting====
@@ Line 89: / Line 159: @@
 ===Displaying===
+Because we already have the debug function, we can use that to display all of the hex values needed
+The format is identical for every address, and goes as the following: [address]:value
+We can print the brackets and colon manually and leave the address and values to the debug function
+<code>
+mov   R3,         91          ;ASCII code for '['
+out   GPUREGION,  R3
+mov   R3,         0           ;Xpos
+out   XDRAWINGP,  R5
+out   GPUCOMMAND, DRAWREGION  ;Draw
+</code>
+Repeat this for ']' and ':' changing the Xpos and accounting for the address width
+Utilize the debug function to print the address and value as shown in the following
+<code>
+push  R2                      ;R2 is the current address
+mov   R3,         10          ;Xpos
+push  R3
+push  R4                      ;Ypos
+call  _debug
+mov   R3,         [R2]        ;Get the value
+push  R3
+mov   R3,         130         ;Xpos
+push  R3
+push  R4                      ;Ypos
+call  _debug
+</code>
+All of this code should be run for every address, stepping from the start value to the end value
+We will need to setup a loop with an exit condition
+===pseudocode===
+<code>
+MOVE THE STARTING ADDRESS INTO A DEDICATED REGISTER (current address)
+UNTIL WE HAVE PASSED THE FINAL ADDRESS:
+   TEST IF THE CURRENT ADDRESS IS GREATER THAN THE FINAL ADDRESS
+      SHOULD IT BE GREATER SKIP TO AFTER THIS LOOP
+   DISPLAY THE ADDRESS AND VALUE
+   INCREMENT THE YPOS
+   INCREMENT THE ADDRESS
+REPEAT
+</code>
 ======debugregister function======
 =====dapX imagery=====
@@ Line 99: / Line 217: @@
 {{:notes:comporg:spring2024:projects:3.jpg?400|}}
 {{:notes:comporg:spring2024:projects:4.jpg?400|}}
+====dap1====
+{{:notes:comporg:spring2024:projects:3.jpg?400|}}
+{{:notes:comporg:spring2024:projects:4.jpg?400|}}
+====dap2====
+{{:notes:comporg:spring2024:projects:5.jpg?400|}}
+{{:notes:comporg:spring2024:projects:6.jpg?400|}}
 ======Debug Registers======

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