glm94/pdp7-unix
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

More notes on the assembly syntax.

Browse Source
This commit is contained in:
Warren Toomey
2016-02-25 07:52:26 +10:00
parent 1bce0d48e3
commit c6a928b8b4
1 changed files with 10 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files
misc/asm_syntax.txt
+10 -4
View File
@@ -5,7 +5,8 @@ Lines starting with " are comment lines
. is the location counter, where the next code or constant will be placed . is the location counter, where the next code or constant will be placed
.. is the relocation counter .. is the relocation counter
t = 0 No idea on this yet t = 0 Sets a built-in variable to this value without generating any machine code.
Variables so far are . .. and t. Not sure what t's purpose is yet.
orig: is a label. It looks like labels can have dots in them. orig: is a label. It looks like labels can have dots in them.
Dots seem to separate structures and fields, e.g. u.base Dots seem to separate structures and fields, e.g. u.base
@@ -14,22 +15,27 @@ orig: is a label. It looks like labels can have dots in them.
jms copy; 10; u.rg+2; 6 Semicolons separate instructions and jms copy; 10; u.rg+2; 6 Semicolons separate instructions and
word expressions that follow the instruction word expressions that follow the instruction
Some expressions are 0:0, not sure about this Some expressions are 0:0, not sure about this.
Is it two 9-bit fields? No idea
jmp 1f Jump back to the closest 1: label jmp 1f Jump back to the closest 1: label
jmp 1b Jump forward to the closest 1: label jmp 1b Jump forward to the closest 1: label
I'm not sure why some lines are indented differently to others e.g. Some lines are indented differently to others e.g.
jms betwen; o10000; o17762 jms betwen; o10000; o17762
jms error jms error
dac .+1 dac .+1
I think this is to indicate the skip logic, but it plays no part in the assembly syntax.
-1 occurs instead of instructions, so it looks like the assembler allows -1 occurs instead of instructions, so it looks like the assembler allows
literal constants at any time. literal constants at any time.
String literals seem to be two characters decorated with < > characters, e.g. String literals seem to be two characters decorated with < > characters, e.g.
"ab" is <a>b. I'm guessing these are placed as pairs in one word. "ab" is <a>b. I'm guessing these are placed as pairs in one word. The syntax
is confusing, because I've also seen <no> ; 040 ; <fi> ; <le>; <s 012 which
appears to mean "no files\n".
Looks like a line can contain multiple labels, e.g. o12: d10: 10 Looks like a line can contain multiple labels, e.g. o12: d10: 10