symbols in _WORD_, 68K bit div, 8080 code assembles?, a couple more

[splitstack-runtimelib/splitstack-runtimelib.git] / runt8080DE.asm

diff --git a/runt8080DE.asm b/runt8080DE.asm
index 4a4b127..51ffa21 100644 (file)
--- a/runt8080DE.asm
+++ b/runt8080DE.asm
@@ -1,10 +1,14 @@
        OPT PRT
 
-; runtimelib FOR 8080
+; runtimelib FOR 8080 using DE as the parameter stack pointer
 ; Joel Matthew Rees September 2020
 
 ; Borrowing some concepts from fig-Forth.
 ; Not tested!
+; In fact, I was never all that good with 8080 code, 
+; and it has been almost 40 years, so ...
+;     don't expect it to work without fixing it.
+; Patterned after 6800 libs.
 
 ; ------------------------------------LICENSE-------------------------------------
 ;
@@ -98,6 +102,21 @@ UP: DS ADRWDSZ      ; pointer to the per-task heap -- BC?
 ; IXSRC:       DS ADRWDSZ      ; source index pointer
 ; IXTERM:      DS ADRWDSZ      ; terminator for moves
 
+; ****
+; Any
+; Using DE for the parameter stack pointer means that
+; interrupts must *not* use the interrupted routine's parameter stack.
+;
+; If we used DE as the stack pointer, it could remain constant while HL indexed the stack.
+; But since we are indexing the stack with the stack pointer itself, 
+; the stack pointer will often be out of position to protect the active contents.
+;
+; We could gamble and guess that six bytes or sixteen would be enough to avoid active stack,
+; but it will be better to just have the interrupt routines set their own parameter stacks.
+; 
+; Note that using DE as the stack pointer would not mean we could use XCHG
+; to save the current pointer and index the stack, for reasons evident from the above.
+; ****