8086asm: now enough tooling to assemble a PC/AT Hello World boot

Verified against nasm with equivalent code.

blk/001

@@ -9,7 +9,7 @@ MASTER INDEX
 490 TRS-80 Recipe             520 Fonts
 550 TI-84+ Recipe             580 RC2014 Recipe
 620 Sega Master System Recipe
-650 AVR assembler
+650 AVR assembler             730 8086 assembler
 
 
 

blk/730

@@ -0,0 +1,16 @@
+8086 assembler
+
+Work in progress. Load with "750 LOAD".
+
+Test code at B731
+
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+

blk/731

@@ -0,0 +1,12 @@
+H@ ORG !
+JMP8, L1 FWR8 ( start )
+L2 BSET ( msg ) ," Hello, World!" 0 A,
+L1 FSET ( start )
+CLI, AH 0 MOVri, AL 2 MOVri, 0x10 INT,
+SI L2 @ ( msg ) MOVrI, AH 0x0e MOVri,
+L1 BSET ( loop ) LODSB, AL AL ORrr,
+JZ, L2 FWR8 ( next ) 0x10 INT,
+JMP8, L1 ( loop ) BWR
+L2 FSET ( next ) AH 0 MOVri, 0x16 INT,
+AH 0x0e MOVri, 0x16 INT, HLT,
+PC ORG @ DUMP

blk/750

@@ -0,0 +1 @@
+1 5 LOADR+

blk/751

@@ -0,0 +1,6 @@
+VARIABLE ORG
+VARIABLE L1 VARIABLE L2 VARIABLE L3 VARIABLE L4
+: AL 0 ; : CL 1 ; : DL 2 ; : BL 3 ;
+: AH 4 ; : CH 5 ; : DH 6 ; : BH 7 ;
+: AX 8 ; : CX 9 ; : DX 10 ; : BX 11 ;
+: SP 12 ; : BP 13 ; : SI 14 ; : DI 15 ;

blk/752

@@ -0,0 +1,8 @@
+( Splits word into msb/lsb, lsb being on TOS )
+: SPLITB
+    256 /MOD SWAP
+;
+: PC H@ ORG @ - ;
+: A, C, ;
+( dst8 src8 -- modrm )
+: MODRMrr 0x7 AND 3 LSHIFT SWAP 0x7 AND OR 0xc0 OR ;

blk/753

@@ -0,0 +1,7 @@
+: MOVri, SWAP 0xb0 OR A, A, ;
+: MOVrI, SWAP 0xb0 OR A, SPLITB A, A, ;
+: INT, 0xcd A, A, ;
+( no argument, flow ops are special )
+: JMP8, 0xeb A, ; : JMP16, 0xe9 A, ; : JZ, 0x74 A, ;
+: LODSB, 0xac A, ; : CLI, 0xfa A, ; : HLT, 0xf4 A, ;
+: ORrr, 0x08 A, MODRMrr A, ;

blk/754

@@ -0,0 +1,16 @@
+( Place BEGIN, where you want to jump back and AGAIN after
+  a relative jump operator. Just like BSET and BWR. )
+: BEGIN, PC ;
+: BSET PC SWAP ! ;
+( same as BSET, but we need to write a placeholder )
+( : FJR, PC 0 A, ;
+: IFZ, JRNZ, FJR, ;
+: IFNZ, JRZ, FJR, ;
+: IFC, JRNC, FJR, ;
+: IFNC, JRC, FJR, ; )
+: THEN,
+    DUP PC          ( l l pc )
+    -^ 1-           ( l off )
+    ( warning: l is a PC offset, not a mem addr! )
+    SWAP ORG @ + ( BIN( @ - ) ( off addr )
+    C! ;

blk/755

@@ -0,0 +1,9 @@
+: FWR8 BSET 0 A, ;
+: FSET @ THEN, ;
+( : BREAK, FJR, 0x8000 OR ;
+: BREAK?, DUP 0x8000 AND IF
+        0x7fff AND 1 ALLOT THEN, -1 ALLOT
+    THEN ; )
+: AGAIN, ( BREAK?, ) PC - 1- A, ;
+: BWR @ AGAIN, ;
+