mirror of
https://github.com/fadden/6502bench.git
synced 2024-11-26 06:49:19 +00:00
Add scripts and inline data to tutorials
Added an inline data formatting section to Tutorial2. Added a new section on extension scripts, using Scripts/Sample as the code.
This commit is contained in:
Andy McFadden
parent
1844fcb8b7
commit
eb99a716f1
Binary file not shown.
@ -53,7 +53,10 @@ stringtab
|
||||
dw string3
|
||||
|
||||
copydone
|
||||
lda #$ff
|
||||
jsr PrintInlineZString
|
||||
asc 'Embedded!',00
|
||||
|
||||
lda #$ff ;self-modifying code example
|
||||
sta _mod+1
|
||||
_mod lda #$00
|
||||
bne skipbrk
|
||||
@ -62,12 +65,12 @@ middat ds 4
|
||||
outdat ds 1
|
||||
|
||||
skipbrk
|
||||
lda middat
|
||||
lda middat ;nearby-label example
|
||||
ora middat+1
|
||||
and middat+2
|
||||
eor middat+3
|
||||
|
||||
ldx #$00
|
||||
ldx #$00 ;embedded instruction example
|
||||
dfb $2c
|
||||
rebr ldx #$01
|
||||
sta outdat
|
||||
@ -85,3 +88,27 @@ thing
|
||||
lda INPUT
|
||||
rts
|
||||
|
||||
PrintInlineZString
|
||||
pla
|
||||
sta PTR1
|
||||
pla
|
||||
sta PTR1+1
|
||||
ldy #$01
|
||||
:loop lda (PTR1),Y
|
||||
beq strend
|
||||
ora #$80
|
||||
jsr $FDED
|
||||
iny
|
||||
bne :loop
|
||||
|
||||
strend tya
|
||||
clc
|
||||
adc PTR1
|
||||
sta PTR1
|
||||
lda PTR1+1
|
||||
adc #$00
|
||||
pha
|
||||
lda PTR1
|
||||
pha
|
||||
rts
|
||||
|
||||
|
||||
@ -22,6 +22,7 @@ manual is recommended.</p>
|
||||
<li><a href="#basic-features">#1: Basic Features</a></li>
|
||||
<li><a href="#advanced-features">#2: Advanced Features</a></li>
|
||||
<li><a href="#address-table">#2a: Address Table Formatting</a></li>
|
||||
<li><a href="#extension-scripts">#2b: Extension Scripts</a></li>
|
||||
</ul>
|
||||
|
||||
|
||||
@ -410,9 +411,9 @@ went well, the operands should now read <code>LDA #<XDATA</code>
|
||||
and <code>LDA #>XDATA</code>.</p>
|
||||
<p>Let's give the pointer a name. Select line $203d, and use
|
||||
Actions > Create Local Variable Table to create an empty table.
|
||||
Click "New Symbol" on the right side. Set the Label field to "PTR1",
|
||||
the Value field to $02, and the width to 2 (it's a 2-byte pointer). Leave
|
||||
the Address button selected. Click "OK" to create the entry, and then
|
||||
Click "New Symbol" on the right side. Leave the Address button selected.
|
||||
Set the Label field to "PTR1", the Value field to $02, and the width
|
||||
to 2 (it's a 2-byte pointer). Click "OK" to create the entry, and then
|
||||
"OK" to update the table.</p>
|
||||
<p>There's now a ".var" statement (similar to a .equ) above line $203d,
|
||||
and the stores to $02/$03 have changed to "PTR1" and "PTR1+1".</p>
|
||||
@ -460,18 +461,42 @@ means the zero-flag is clear.)</p>
|
||||
you add an end-of-line comment, it appears after the cycle count.</p>
|
||||
<p>Hit Ctrl+S to save your project. Make that a habit.</p>
|
||||
|
||||
<h4>Inline Data</h4>
|
||||
|
||||
<p>Consider the code at address $206B. It's a JSR followed by some
|
||||
ASCII text, then a $00 byte, and then what might be code. Double-click
|
||||
on the JSR opcode to jump to $20AB to see the function. It pulls the
|
||||
call address off the stack, and uses it as a pointer. When it encounters
|
||||
a zero byte, it breaks out of the loop, pushes the adjusted pointer
|
||||
value back onto the stack, and returns.</p>
|
||||
<p>This is an example of "inline data", where a function uses the return
|
||||
address to get a pointer to data. The return address is adjusted to
|
||||
point past the inline data before returning (technically, it points at
|
||||
the very last byte of the inline data, because RTS jumps to address + 1).</p>
|
||||
<p>To format the data, we first need to tell SourceGen that there's data
|
||||
in line with the code. Select the line at address $206E, then
|
||||
shift-click the line at address $2077. Use Actions > Hint as Inline Data.</p>
|
||||
<p>The data turns to single-byte values, and we now see the code
|
||||
continuing at address $2078. We can format the data as string by
|
||||
using Actions > Edit Operand, setting the Character Encoding to "Low or
|
||||
High ASCII", and choosing "null-terminated strings".</p>
|
||||
|
||||
<p>That's pretty straightforward, but this could quickly become tedious if
|
||||
there were a lot of these. SourceGen allows you to define scripts to
|
||||
automate common formatting tasks. This is covered in a later tutorial.</p>
|
||||
|
||||
<h4>Odds & Ends</h4>
|
||||
|
||||
<p>The rest of the code isn't really intended to do anything useful. It
|
||||
just exists to illustrate some odd situations.</p>
|
||||
<p>Look at the code starting at $206b. It ends with a BRK at $2074, which
|
||||
<p>Look at the code starting at $2078. It ends with a BRK at $2081, which
|
||||
as noted earlier is a bad sign. If you look two lines above the BRK,
|
||||
you'll see that it's loading the accumulator with zero, then doing a BNE,
|
||||
which should never be taken (note the cycle count for the BNE is 2). The
|
||||
trick is in the two lines before that, which use self-modifying code to
|
||||
change the LDA immediate operand from $00 to $ff. The BNE is actually
|
||||
a branch-always.</p>
|
||||
<p>We can fix this by correcting the status flags. Select line $2072,
|
||||
<p>We can fix this by correcting the status flags. Select line $207F,
|
||||
and then Actions > Override Status Flags. This lets us specify what
|
||||
the flags should be before the instruction is executed. For each flag,
|
||||
we can override the default behavior and specify that the flag is
|
||||
@ -481,13 +506,13 @@ in the "Z" column click on the button in the "Zero" row. Click "OK". The
|
||||
BNE is now an always-taken branch, and the code list rearranges itself
|
||||
appropriately (and the cycle count is now 3).</p>
|
||||
|
||||
<p>Continuing on, the code at $2079 touches a few consecutive locations. Edit
|
||||
the label on line $2074, setting it to "STUFF". Notice how the references
|
||||
to $2074 through $2077 have changed from auto-generated labels to
|
||||
<p>Continuing on, the code at $2086 touches a few consecutive locations. Edit
|
||||
the label on line $2081, setting it to "STUFF". Notice how the references
|
||||
to $2081 through $2084 have changed from auto-generated labels to
|
||||
references to STUFF. For some projects this may be undesirable. Use
|
||||
Edit > Project Properties, then in the Analysis Parameters box
|
||||
un-check "Seek nearby targets", and click "OK". You'll notice that the
|
||||
references to $2075 and later have switched back to auto labels. If
|
||||
references to $2081 and later have switched back to auto labels. If
|
||||
you scroll up, you'll see that the references to PTR1+1 and PTR2+1 were
|
||||
not affected, because local variables use explicit widths rather
|
||||
than the "nearby" logic.</p>
|
||||
@ -495,7 +520,7 @@ than the "nearby" logic.</p>
|
||||
avoid explicitly labeling every part of a multi-byte data item. For now,
|
||||
use Edit > Undo to switch it back on.</p>
|
||||
|
||||
<p>The code at $2085 looks a bit strange. <code>LDX</code>, then a
|
||||
<p>The code at $2092 looks a bit strange. <code>LDX</code>, then a
|
||||
<code>BIT</code> with a weird symbol, then another <code>LDX</code>. If
|
||||
you look at the "bytes" column, you'll notice that the three-byte
|
||||
<code>BIT</code> instruction has only one byte on its line. The
|
||||
@ -503,7 +528,7 @@ trick here is that the <code>LDX #$01</code> is embedded inside the
|
||||
<code>BIT</code> instruction. When the code runs through here, X is set
|
||||
to $00, then the <code>BIT</code> instruction sets some flags, then the
|
||||
<code>STA</code> runs. Several lines down there's a <code>BNE</code>
|
||||
to $2088, which is in the middle of the <code>BIT</code> instruction.
|
||||
to $2095, which is in the middle of the <code>BIT</code> instruction.
|
||||
It loads X with $01, then also continues to the <code>STA</code>.</p>
|
||||
<p>Embedded instructions are unusual but not unheard-of. (This trick is
|
||||
used extensively in Microsoft BASICs, such as Applesoft.) When you see the
|
||||
@ -513,9 +538,7 @@ on.</p>
|
||||
|
||||
<h2><a name="address-table">Tutorial #2a: Address Table Formatting</a></h2>
|
||||
|
||||
<p>This tutorial covers one specific feature.</p>
|
||||
|
||||
<h3>Formatting a Split-Address Table</h3>
|
||||
<p><i>This tutorial covers one specific feature.</i></p>
|
||||
|
||||
<p>Start a new project. Select the Apple //e platform, click Select File
|
||||
and navigate to the Examples directory. In A2-Amper-fdraw, select
|
||||
@ -588,6 +611,59 @@ code entry point hint -- but did several of them at once.</p>
|
||||
SourceGen asks for confirmation, click Discard & Continue.</p>
|
||||
|
||||
|
||||
<h2><a name="extension-scripts">Tutorial #2b: Extension Scripts</a></h2>
|
||||
|
||||
<p><i>This tutorial covers one specific feature.</i></p>
|
||||
|
||||
<p>Some repetitive formatting tasks can be handled with automatic scripts.
|
||||
This is especially useful for inline data, which confuses the disassembler
|
||||
because code is expected.</p>
|
||||
<p>An earlier tutorial demonstrated how to manually mark bytes as
|
||||
inline data. We're going to do it a faster way. For this tutorial,
|
||||
start a new project with "Generic 6502", and in the SourceGen
|
||||
installation directory find the Examples directory, open the Scripts
|
||||
subdirectory, and select "Sample".</p>
|
||||
<p>We'll need to load scripts from the project directory, so we have to
|
||||
save the project. File > Save, call it the default name (Sample.dis65).</p>
|
||||
|
||||
<p>Take a look at the disassembly listing. The file starts with a JSR
|
||||
followed by a string that begins with a small number. This appears to be
|
||||
a string with a leading length byte. We want to load a script that
|
||||
can handle that, so use Edit > Project Properties, select the
|
||||
Extension Scripts tab, click "Add Scripts from Project", and then
|
||||
the file "InlineL1String.cs". Click OK.</p>
|
||||
<p>Nothing happened. If you look at the script (and you know some C#),
|
||||
you'll see that it's looking for a JSR to a function called
|
||||
"PrintInlineL1String". So let's give it one.</p>
|
||||
<p>Double-click the JSR operand ("L1026"), click "Create Label", and
|
||||
enter "PrintInlineL1String". Remember that labels are case-sensitive;
|
||||
you must enter it exactly as shown. Hit OK to accept the label, and OK
|
||||
to close the operand editor. If all went well, address $1003 should now be
|
||||
an L1 string "How long?", and adress $100D should be another JSR.</p>
|
||||
|
||||
<p>The next JSR appears to be followed by a null-terminated string, so
|
||||
we'll need something that handles that. Go back into Project Properties
|
||||
and add the script "InlineNullTermString.cs".</p>
|
||||
<p>This script is slightly different, in that it handles any JSR to a label
|
||||
that starts with "PrintInlineNullString". So let's give it a couple of
|
||||
those.</p>
|
||||
<p>Double-click the operand on line $100D ("L1027"), click Create Label,
|
||||
and set the label to "PrintInlineNullStringOne". Hit OK twice. That
|
||||
formatted the first one and got us to the next JSR. Repeat the process
|
||||
on line $1019 ("L1028"), setting the label to "PrintInlineNullStringTwo".</p>
|
||||
|
||||
<p>The entire project is now nicely formatted. In a real project the
|
||||
"Print Inline" locations would be actual print functions, not just RTS
|
||||
instructions, and there would be multiple JSRs to a single function.
|
||||
So labeling a single print function could format dozens of inline strings
|
||||
and clean up the disassembly automatically.</p>
|
||||
|
||||
<p>Extension scripts can make your life much easier, but they do require
|
||||
some programming experience. See the
|
||||
<a href="advanced.html#extension-scripts">manual</a> for more details.</p>
|
||||
|
||||
|
||||
|
||||
<h2>End of Tutorials</h2>
|
||||
|
||||
<p>That's it for the tutorials. Significantly more detail on
|
||||
|
||||
Loading…
Reference in New Issue
Block a user