8086asm: properly initialize DS and DF

Verified against nasm with equivalent code.

blk/001

@@ -10,7 +10,7 @@ MASTER INDEX
 550 TI-84+ Recipe             580 RC2014 Recipe
 620 Sega Master System Recipe
 650 AVR assembler             730 8086 assembler
-
+810 PC/AT Recipe
 
 
 

blk/730

@@ -2,7 +2,7 @@
 
 Work in progress. Load with "750 LOAD".
 
-Test code at B731
+
 
 
 

blk/731

@@ -1,2 +0,0 @@
-AH 0x42 MOVri,
-8 H@ 2 - DUMP

blk/750

@@ -1 +1 @@
-1 3 LOADR+
+1 5 LOADR+

blk/751

@@ -1,5 +1,8 @@
 VARIABLE ORG
+CREATE BIN( 0 , : BIN(+ BIN( @ + ;
+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 ;
+: ES 0 ; : CS 1 ; : SS 2 ; : DS 3 ;

blk/752

@@ -1,2 +1,8 @@
-: PC H@ ORG @ - ;
+( Splits word into msb/lsb, lsb being on TOS )
+: SPLITB
+    256 /MOD SWAP
+;
+: PC H@ ORG @ - BIN( @ + ;
 : A, C, ;
+( dst8 src8 -- modrm )
+: MODRMrr 0x7 AND 3 LSHIFT SWAP 0x7 AND OR 0xc0 OR ;

blk/753

@@ -1 +1,10 @@
 : MOVri, SWAP 0xb0 OR A, A, ;
+: MOVrI, SWAP 0xb0 OR A, SPLITB A, A, ;
+: MOVsx, 0x8e A, SWAP MODRMrr 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, ;
+: XORxx, 0x31 A, MODRMrr A, ;
+: CLD, 0xfc A, ; : STD, 0xfd 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, ;
+

blk/810

@@ -0,0 +1,5 @@
+PC/AT Recipe
+
+Work in progress.
+
+811 Hello World boot

blk/811

@@ -0,0 +1,14 @@
+: _filler 510 H@ ORG @ - DO 0 A, LOOP 0x55 A, 0xaa A, ;
+H@ ORG ! 0x7c00 BIN( ! ( BIOS loads boot bin at 0x7c00 )
+JMP8, L1 FWR8 ( start )
+L2 BSET ( msg ) ," Hello, World!" 0 A,
+L1 FSET ( start )
+CLI, CLD, AX AX XORxx, DS AX MOVsx,
+AH 0 MOVri, AL 2 MOVri, ( 80x25 BW video mode ) 0x10 INT,
+SI L2 @ ( msg ) MOVrI, AH 0x0e MOVri, ( print char )
+L1 BSET ( loop ) LODSB, AL AL ORrr, ( end of str? )
+JZ, L2 FWR8 ( next ) 0x10 INT, ( print char )
+JMP8, L1 ( loop ) BWR
+L2 FSET ( next ) AH 0 MOVri, 0x16 INT, ( read kbd )
+AH 0x0e MOVri, 0x10 INT, ( spit read char ) HLT, ( done )
+_filler

recipes/pcat/Makefile

@@ -0,0 +1,16 @@
+TARGET = boot.bin
+BASEDIR = ../..
+EDIR = $(BASEDIR)/emul
+STAGE = $(EDIR)/stage
+
+.PHONY: all
+all: $(TARGET) 
+$(TARGET): xcomp.fs $(STAGE)
+	cat xcomp.fs | $(STAGE) > $@
+
+$(STAGE):
+	$(MAKE) -C $(EDIR) stage
+
+.PHONY: emul
+emul: $(TARGET)
+	qemu-system-i386 -fda $(TARGET)

recipes/pcat/README.md

@@ -0,0 +1,3 @@
+# PC/AT recipe
+
+Work in progress.

recipes/pcat/xcomp.fs

@@ -0,0 +1,4 @@
+750 LOAD
+811 LOAD
+ORG @ 256 /MOD 2 PC! 2 PC!
+H@ 256 /MOD 2 PC! 2 PC!