blk/001

@@ -6,6 +6,7 @@ MASTER INDEX
 150 Extra words
 200 Z80 assembler             260 Cross compilation
 280 Z80 boot code             390 Cross-compiled core
+439 XPACKed core              
 490 TRS-80 Recipe             520 Fonts
 550 TI-84+ Recipe             580 RC2014 Recipe
 

blk/043

@@ -12,5 +12,4 @@ have to consume it to avoid PSP leak.
 ]         --   End interpretative mode.
 ABORT     --   Resets PS and RS and returns to interpreter.
 ABORT" x" --   *I* Compiles a ." followed by a ABORT.
-ERR       a -- Prints a and ABORT. Defined early and used by
-               drivers.                                 (cont.)
+EXECUTE   a -- Execute wordref at addr a

blk/044

@@ -1,4 +1,3 @@
-EXECUTE   a -- Execute wordref at addr a
 INTERPRET --   Get a line from stdin, compile it in tmp memory,
                then execute the compiled contents.
 LEAVE     --   In a DO..LOOP, exit at the next LOOP call.

blk/263

@@ -1,13 +1,14 @@
 VARIABLE XCURRENT
+
 : XCON XCURRENT CURRENT* ! ;
 : XCOFF 0x02 RAM+ CURRENT* ! ;
+
 : (xentry) XCON (entry) XCOFF ;
 : XCREATE (xentry) 11 C, ;
 : XCODE XCON CODE XCOFF ;
 : XIMM XCON IMMEDIATE XCOFF ;
 : _xapply ( a -- a-off )
     DUP ORG @ > IF ORG @ - BIN( @ + THEN ;
-: X' XCON ' XCOFF ;
 : X['] XCON ' _xapply LITA XCOFF ;
 : XCOMPILE
     XCON ' _xapply LITA

blk/394

@@ -1,5 +1,4 @@
 : ABORT (resSP) QUIT ;
-: ERR LIT< (print) (find) IF EXECUTE THEN ABORT ;
 : = CMP NOT ; : < CMP -1 = ; : > CMP 1 = ;
 : 0< 32767 > ; : >= < NOT ; : <= > NOT ; : 0>= 0< NOT ;
 ( n l h -- f )

blk/409

@@ -1,16 +1,7 @@
-( Words here until the end of the low part, unlike words
-  preceeding them, aren't immediately needed for boot. But its
-  better to have as many words as possible in the xcomp part. )
-: H@ HERE @ ;
-: IMMEDIATE
-    CURRENT @ 1-
-    DUP C@ 128 OR SWAP C! ;
-: IMMED? 1- C@ 0x80 AND ;
-: +! SWAP OVER @ + SWAP ! ;
-: -^ SWAP - ;
-: / /MOD SWAP DROP ;
-: MOD /MOD DROP ;
-: ALLOT HERE +! ;
-: CREATE (entry) 11 ( 11 == cellWord ) C, ;
-: VARIABLE CREATE 2 ALLOT ;
-: LEAVE R> R> DROP I 1- >R >R ;
+: INTERPRET
+    BEGIN
+    WORD DUP C@ EOT? IF DROP EXIT THEN
+    (find)
+    NOT IF (parse) ELSE EXECUTE THEN
+    C<? NOT IF LIT< (ok) (find) IF EXECUTE THEN THEN
+    AGAIN ;

blk/410

@@ -1,13 +1,11 @@
-: '? WORD (find) ;
-: '
-    '? (?br) [ 4 , ] EXIT
-    LIT< (wnf) (find) DROP EXECUTE
+( system c< simply reads source from binary, starting at
+  LATEST. Convenient way to bootstrap a new system. )
+: (boot<)
+    ( 2e == BOOT C< PTR )
+    0x2e RAM+ @   ( a )
+    DUP C@        ( a c )
+    SWAP 1 +      ( c a+1 )
+    0x2e RAM+ !   ( c )
 ;
-: ROLL
-    DUP NOT IF EXIT THEN
-    1+ DUP PICK          ( n val )
-    SWAP 2 * (roll)      ( val )
-    SWAP DROP
-;
-: 2OVER 3 PICK 3 PICK ;
-: 2SWAP 3 ROLL 3 ROLL ;
+
+

blk/411

@@ -1,13 +1,13 @@
-: MOVE ( a1 a2 u -- )
-    ( u ) 0 DO ( a1 a2 )
-        SWAP C@+ ( a2 a1+1 x )
-        ROT C!+ ( a1+1 a2+1 )
-    LOOP 2DROP ;
-: MOVE- ( a1 a2 u -- )
-    SWAP OVER + 1- ( a1 u a2+u-1 )
-    ROT 2 PICK + 1- ( u a2+u-1 a1+u-1 )
-    ROT ( u ) 0 DO ( a2 a1 )
-        C@- ( a2 a1-1 x )
-        ROT C!- ( a1-1 a2-1 ) SWAP ( a2 a1 )
-    LOOP 2DROP ;
-: PREV 3 - DUP @ - ;
+: BOOT
+    0x02 RAM+ CURRENT* !
+    CURRENT @ 0x2e RAM+ ! ( 2e == BOOT C< PTR )
+    0 0x08 RAM+ !  ( 08 == C<* override )
+    0 0x53 RAM+ !  ( 53 == (emit) override )
+    0 0x55 RAM+ !  ( 55 == (key) override )
+    0 0x0a RAM+ !  ( NLPTR )
+    ( 0c == C<* )
+    ['] (boot<) 0x0c RAM+ !
+    ( boot< always has a char waiting. 06 == C<?* )
+    1 0x06 RAM+ !
+    INTERPRET BYE ;
+

blk/412

@@ -1,13 +1,16 @@
-: WORD(
-    DUP 1- C@   ( name len field )
-    127 AND     ( 0x7f. remove IMMEDIATE flag )
-    3 +         ( fixed header len )
-    -
-;
-: FORGET
-    ' DUP               ( w w )
-    ( HERE must be at the end of prev's word, that is, at the
-      beginning of w. )
-    WORD( HERE !  ( w )
-    PREV CURRENT !
+( Words here until the end of the low part, unlike words
+  preceeding them, aren't immediately needed for boot. But its
+  better to have as many words as possible in the xcomp part. )
+: H@ HERE @ ;
+: IMMEDIATE
+    CURRENT @ 1-
+    DUP C@ 128 OR SWAP C!
 ;
+: +! SWAP OVER @ + SWAP ! ;
+: -^ SWAP - ;
+: / /MOD SWAP DROP ;
+: MOD /MOD DROP ;
+
+: ALLOT HERE +! ;
+: CREATE (entry) 11 ( 11 == cellWord ) C, ;
+: LEAVE R> R> DROP I 1- >R >R ;

blk/413

@@ -1,15 +1,13 @@
-: DOES>
-    ( Overwrite cellWord in CURRENT )
-    ( 43 == doesWord )
-    43 CURRENT @ C!
-    ( When we have a DOES>, we forcefully place HERE to 4
-      bytes after CURRENT. This allows a DOES word to use ","
-      and "C," without messing everything up. )
-    CURRENT @ 3 + HERE !
-    ( HERE points to where we should write R> )
-    R> ,
-    ( We're done. Because we've popped RS, we'll exit parent
-      definition )
+: '? WORD (find) ;
+: '
+    '? (?br) [ 4 , ] EXIT
+    LIT< (wnf) (find) DROP EXECUTE
 ;
-: CONSTANT CREATE , DOES> @ ;
-
+: ROLL
+    DUP NOT IF EXIT THEN
+    1+ DUP PICK          ( n val )
+    SWAP 2 * (roll)      ( val )
+    SWAP DROP
+;
+: 2OVER 3 PICK 3 PICK ;
+: 2SWAP 3 ROLL 3 ROLL ;

blk/414

@@ -1,5 +1,13 @@
-: [IF]
-    IF EXIT THEN
-    LIT< [THEN] BEGIN DUP WORD S= UNTIL DROP ;
-: [THEN] ;
-
+: MOVE ( a1 a2 u -- )
+    ( u ) 0 DO ( a1 a2 )
+        SWAP C@+ ( a2 a1+1 x )
+        ROT C!+ ( a1+1 a2+1 )
+    LOOP 2DROP ;
+: MOVE- ( a1 a2 u -- )
+    SWAP OVER + 1- ( a1 u a2+u-1 )
+    ROT 2 PICK + 1- ( u a2+u-1 a1+u-1 )
+    ROT ( u ) 0 DO ( a2 a1 )
+        C@- ( a2 a1-1 x )
+        ROT C!- ( a1-1 a2-1 ) SWAP ( a2 a1 )
+    LOOP 2DROP ;
+: PREV 3 - DUP @ - ;

blk/415

@@ -0,0 +1,13 @@
+: WORD(
+    DUP 1- C@   ( name len field )
+    127 AND     ( 0x7f. remove IMMEDIATE flag )
+    3 +         ( fixed header len )
+    -
+;
+: FORGET
+    ' DUP               ( w w )
+    ( HERE must be at the end of prev's word, that is, at the
+      beginning of w. )
+    WORD( HERE !  ( w )
+    PREV CURRENT !
+;

blk/420

@@ -1 +1 @@
-1 20 LOADR+ ( xcomp core high )
+1 16 LOADR+ ( xcomp core high )

blk/421

@@ -1,16 +1,14 @@
 : EMIT
     ( 0x53==(emit) override )
     0x53 RAM+ @ DUP IF EXECUTE ELSE DROP (emit) THEN ;
+
 : (print)
     BEGIN
         C@+      ( a+1 c )
         ( exit if null or 0xd )
         DUP 0xd = OVER NOT OR IF 2DROP EXIT THEN
         EMIT     ( a )
-    AGAIN ;
-: BS 8 EMIT ; : LF 10 EMIT ; : CR 13 EMIT ;
-: CRLF CR LF ; : SPC 32 EMIT ;
-: NL 0x0a RAM+ @ ( NLPTR ) DUP IF EXECUTE ELSE DROP CRLF THEN ;
-: (ok) SPC LIT" ok" (print) NL ;
-: (uflw) LIT" stack underflow" ERR ;
-: (wnf) (print) SPC LIT" word not found" ERR ;
+    AGAIN
+;
+
+

blk/422

@@ -1,7 +1,15 @@
 : ,"
     BEGIN
-        C< DUP 34 ( ASCII " ) = IF DROP EXIT THEN C,
+        C<
+        ( 34 is ASCII for " )
+        DUP 34 = IF DROP EXIT THEN C,
     AGAIN ;
-: LIT" 34 , ( litWord ) ," 0 C, ; IMMEDIATE
-: ." [COMPILE] LIT" COMPILE (print) ; IMMEDIATE
+
+: ."
+    34 , ( 34 == litWord ) ," 0 C,
+    COMPILE (print)
+; IMMEDIATE
 : ABORT" [COMPILE] ." COMPILE ABORT ; IMMEDIATE
+: BS 8 EMIT ; : LF 10 EMIT ; : CR 13 EMIT ;
+: CRLF CR LF ; : SPC 32 EMIT ;
+: NL 0x0a RAM+ @ ( NLPTR ) DUP IF EXECUTE ELSE DROP CRLF THEN ;

blk/432

@@ -1,14 +1,3 @@
-: INTERPRET
-    BEGIN
-    WORD DUP C@ EOT? IF DROP EXIT THEN
-    (find) NOT IF (parse) ELSE EXECUTE THEN
-    C<? NOT IF (ok) THEN
-    AGAIN ;
-( Read from BOOT C< PTR and inc it. )
-: (boot<)
-    ( 2e == BOOT C< PTR )
-    0x2e ( BOOT C< PTR ) RAM+ @ DUP C@ ( a c )
-    SWAP 1 + 0x2e RAM+ ! ( c ) ;
 ( pre-comment for tight LOAD: The 0x08==I check after INTERPRET
   is to check whether we're restoring to "_", the word above.
   if yes, then we're in a nested load. Also, the 1 in 0x06 is

blk/435

@@ -0,0 +1,14 @@
+( LITN has to be defined after the last immediate usage of
+  it to avoid bootstrapping issues )
+: LITN 32 , , ( 32 == NUMBER ) ;
+
+: IMMED? 1- C@ 0x80 AND ;
+
+( ';' can't have its name right away because, when created, it
+  is not an IMMEDIATE yet and will not be treated properly by
+  xcomp. )
+: _
+    ['] EXIT ,
+    R> DROP     ( exit : )
+; IMMEDIATE
+

blk/436

@@ -1,13 +1,16 @@
-: BOOT
-    0x02 RAM+ CURRENT* !
-    CURRENT @ 0x2e RAM+ ! ( 2e == BOOT C< PTR )
-    0 0x08 RAM+ !  ( 08 == C<* override )
-    0 0x53 RAM+ !  ( 53 == (emit) override )
-    0 0x55 RAM+ !  ( 55 == (key) override )
-    0 0x0a RAM+ !  ( NLPTR )
-    ( 0c == C<* )
-    ['] (boot<) 0x0c RAM+ !
-    ( boot< always has a char waiting. 06 == C<?* )
-    1 0x06 RAM+ !
-    INTERPRET BYE ;
-
+XCURRENT @ ( to PSP )
+: :
+    (entry)
+    ( We cannot use LITN as IMMEDIATE because of bootstrapping
+      issues. Same thing for ",".
+      32 == NUMBER 14 == compiledWord )
+    [ 32 H@ ! 2 ALLOT 14 H@ ! 2 ALLOT ] C,
+    BEGIN
+        WORD
+        (find)
+        ( is word )
+        IF DUP IMMED? IF EXECUTE ELSE , THEN
+        ( maybe number )
+        ELSE (parse) LITN THEN
+    AGAIN ;
+( from PSP ) ';' SWAP 4 - C!

blk/437

@@ -1,15 +0,0 @@
-( Now we have "as late as possible" stuff )
-: DO COMPILE 2>R H@ ; IMMEDIATE
-: LOOP COMPILE (loop) H@ - , ; IMMEDIATE
-( LEAVE is implemented in low xcomp )
-: LITN 32 , , ( 32 == NUMBER ) ;
-( gets its name at the very end. can't comment afterwards )
-: _ BEGIN LIT< ) WORD S= UNTIL ; IMMEDIATE
-: _ ( : will get its name almost at the very end )
-    (entry)
-    [ 14 ( == compiledWord ) LITN ] C,
-    BEGIN
-        WORD (find)
-        IF ( is word ) DUP IMMED? IF EXECUTE ELSE , THEN
-        ELSE ( maybe number ) (parse) LITN THEN
-    AGAIN ;

blk/438

@@ -1,14 +0,0 @@
-: IF                ( -- a | a: br cell addr )
-    COMPILE (?br) H@ 2 ALLOT ( br cell allot )
-; IMMEDIATE
-: THEN              ( a -- | a: br cell addr )
-    DUP H@ -^ SWAP ( a-H a ) !
-; IMMEDIATE
-: ELSE              ( a1 -- a2 | a1: IF cell a2: ELSE cell )
-    COMPILE (br)
-    2 ALLOT
-    DUP H@ -^ SWAP  ( a-H a )
-    !
-    H@ 2-          ( push a. -2 for allot offset )
-; IMMEDIATE
-

blk/439

@@ -1,9 +1,14 @@
-: BEGIN H@ ; IMMEDIATE
-: AGAIN COMPILE (br) H@ - , ; IMMEDIATE
-: UNTIL COMPILE (?br) H@ - , ; IMMEDIATE
-: [ INTERPRET ; IMMEDIATE
-: ] R> DROP ;
-: LIT< WORD 34 , SCPY 0 C, ; IMMEDIATE
-: LITA 36 , , ;
-: COMPILE ' LITA ['] , , ; IMMEDIATE
-: [COMPILE] ' , ; IMMEDIATE
+XPACKed core
+
+Most of Collapse OS' core words are cross compiled (B390).
+However, some of them are too dynamically referenced to be
+cross-compiled without great pain, so we XPACK (B267) them,
+that is, we put them in source form in the target's
+initialization section (see B89).
+
+These words will be compiled into RAM at initialization, which
+is a bit wasteful both in RAM and in boot time, so we will
+typically relink (B120) that newly compiled binary and append
+it to our existing binary for optimal resource usage.
+
+Load range: 440-446

blk/440

@@ -1,11 +1,10 @@
-( ';' can't have its name right away because, when created, it
-  is not an IMMEDIATE yet and will not be treated properly by
-  xcomp. )
-: _
-    ['] EXIT ,
-    R> DROP     ( exit : )
-; IMMEDIATE
+: [ INTERPRET ; IMMEDIATE
+: ] R> DROP ;
+: LIT< WORD 34 , SCPY 0 C, ; IMMEDIATE
+: LITA 36 , , ;
 : ['] ' LITA ; IMMEDIATE
-';' X' _ 4 - C! ( give ; its name )
-':' X' _ 4 - C! ( give : its name )
-'(' X' _ 4 - C!
+: COMPILE ' LITA ['] , , ; IMMEDIATE
+: [COMPILE] ' , ; IMMEDIATE
+: BEGIN H@ ; IMMEDIATE
+: AGAIN COMPILE (br) H@ - , ; IMMEDIATE
+: UNTIL COMPILE (?br) H@ - , ; IMMEDIATE

blk/441

@@ -0,0 +1,13 @@
+: _ BEGIN LIT< ) WORD S= UNTIL ; IMMEDIATE
+40 CURRENT @ 4 - C!
+( Hello, hello, krkrkrkr... do you hear me?
+  Ah, voice at last! Some lines above need comments
+  BTW: Forth lines limited to 64 cols because of default
+  input buffer size in Collapse OS
+
+  40 is ASCII for '('. We do this to simplify XPACK's task of
+  not mistakenly consider '(' definition as a comment.
+  LIT<: 34 == litWord
+  LITA: 36 == addrWord
+  COMPILE: Tough one. Get addr of caller word (example above
+  (br)) and then call LITA on it. )

blk/442

@@ -0,0 +1,11 @@
+: IF                ( -- a | a: br cell addr )
+    COMPILE (?br)
+    H@              ( push a )
+    2 ALLOT         ( br cell allot )
+; IMMEDIATE
+
+: THEN              ( a -- | a: br cell addr )
+    DUP H@ -^ SWAP   ( a-H a )
+    !
+; IMMEDIATE
+

blk/443

@@ -0,0 +1,12 @@
+: ELSE              ( a1 -- a2 | a1: IF cell a2: ELSE cell )
+    COMPILE (br)
+    2 ALLOT
+    DUP H@ -^ SWAP  ( a-H a )
+    !
+    H@ 2-          ( push a. -2 for allot offset )
+; IMMEDIATE
+
+: [IF]
+    IF EXIT THEN
+    LIT< [THEN] BEGIN DUP WORD S= UNTIL DROP ;
+: [THEN] ;

blk/444

@@ -0,0 +1,14 @@
+: DOES>
+    ( Overwrite cellWord in CURRENT )
+    ( 43 == doesWord )
+    43 CURRENT @ C!
+    ( When we have a DOES>, we forcefully place HERE to 4
+      bytes after CURRENT. This allows a DOES word to use ","
+      and "C," without messing everything up. )
+    CURRENT @ 3 + HERE !
+    ( HERE points to where we should write R> )
+    R> ,
+    ( We're done. Because we've popped RS, we'll exit parent
+      definition )
+;
+

blk/445

@@ -0,0 +1,8 @@
+: VARIABLE CREATE 2 ALLOT ;
+: CONSTANT CREATE , DOES> @ ;
+
+( In addition to pushing H@ this compiles 2>R so that loop
+  variables are sent to PS at runtime )
+: DO COMPILE 2>R H@ ; IMMEDIATE
+: LOOP COMPILE (loop) H@ - , ; IMMEDIATE
+( LEAVE is implemented in xcomp )

blk/446

@@ -0,0 +1,3 @@
+: (ok) SPC ." ok" NL ;
+: (uflw) ABORT" stack underflow" ;
+: (wnf) (print) SPC ABORT" word not found" ;

blk/490

@@ -4,7 +4,8 @@ Support code for the TRS-80 recipe. Contains drivers for the
 keyboard, video and floppy. At the moment, they are thin layer
 over the drivers provided by TRSDOS' SVC.
 
-Load with "492 LOAD".
+Load the Z80 words with "492 LOAD" and the high level part
+with "498 LOAD".
 
 There is also the RECV program at B502 and the XCOMP unit at
 B504

blk/492

@@ -1 +1 @@
-1 8 LOADR+
+1 5 LOADR+

blk/498

@@ -0,0 +1 @@
+1 2 LOADR+

blk/499

@@ -1,4 +1,4 @@
-: _err LIT" FDerr" ERR ;
+: _err ABORT" FDerr" ;
 : _cylsec ( sec -- cs, return sector/cylinder for given secid )
     ( 4 256b sectors per block, 10 sec per cyl, 40 cyl max )
     10 /MOD ( sec cyl )

blk/500

@@ -2,6 +2,6 @@
 : FD! ['] @WRSEC SWAP FD@! ;
 : FD$ ['] FD@ BLK@* ! ['] FD! BLK!* ! ;
 
-: _err LIT" *CLerr" ERR ;
+: _err ABORT" *CLerr" ;
 : *CL< 0 BEGIN DROP 0x0238 @GET UNTIL ;
 : *CL> 0x0238 @PUT NOT IF _err THEN ;

blk/580

@@ -4,4 +4,4 @@ Support code for the RC2014 recipe. Contains drivers for the
 ACIA, SD card and AT28 EEPROM.
 
 581 ACIA                       590 AT28 EEPROM
-600 SD card                    618 Xcomp unit
+600 SD card

blk/618

@@ -1,15 +0,0 @@
-0x8000 CONSTANT RAMSTART
-0xf000 CONSTANT RS_ADDR        0xfffa CONSTANT PS_ADDR
-0x80   CONSTANT ACIA_CTL       0x81   CONSTANT ACIA_IO
-4      CONSTANT SDC_SPI
-5      CONSTANT SDC_CSLOW      6      CONSTANT SDC_CSHIGH
-RAMSTART 0x70 + CONSTANT ACIA_MEM
-212 LOAD  ( z80 assembler )
-262 LOAD  ( xcomp )            270 LOAD  ( xcomp overrides )
-282 LOAD  ( boot.z80 )         393 LOAD  ( xcomp core low )
-582 LOAD  ( acia )
-420 LOAD  ( xcomp core high )
-(entry) _
-( Update LATEST )
-PC ORG @ 8 + !
-," : _ ACIA$ RDLN$ (ok) ; _ "

emul/.gitignore

@@ -1,4 +1,7 @@
-/stage
+/stage1
+/stage1dbg
+/stage2
 /forth
 /*-bin.h
+/stage0.bin
 /blkfs

emul/Makefile

@@ -1,4 +1,4 @@
-TARGETS = forth stage
+TARGETS = forth stage2
 OBJS = emul.o libz80/libz80.o
 BIN2C = ../tools/bin2c
 BLKPACK = ../tools/blkpack
@@ -14,12 +14,24 @@ $(BLKPACK):
 $(BIN2C): $(BLKPACK)
 $(BLKUNPACK): $(BLKPACK)
 
+stage0.bin: stage2 xcomp.fs
+	cat xcomp.fs | ./stage2 > stage0.bin
+
+stage0-bin.h: stage0.bin $(BIN2C)
+	$(BIN2C) KERNEL < stage0.bin > $@
+
+stage1: stage.c $(OBJS) stage0-bin.h 
+	$(CC) stage.c $(OBJS) -o $@
+
+stage1dbg: stage.c $(OBJS) stage0-bin.h 
+	$(CC) -DDEBUG stage.c $(OBJS) -o $@
+
 # not dependent on forth.bin to avoid circular deps.
 forth-bin.h: $(BIN2C)
 	$(BIN2C) KERNEL < forth.bin > $@
 
-stage: stage.c $(OBJS) forth-bin.h blkfs-bin.h
-	$(CC) stage.c $(OBJS) -o $@
+stage2: stage.c $(OBJS) forth-bin.h blkfs-bin.h
+	$(CC) -DSTAGE2 stage.c $(OBJS) -o $@
 
 blkfs: $(BLKPACK)
 	$(BLKPACK) ../blk > $@
@@ -39,8 +51,8 @@ emul.o: emul.c
 
 
 .PHONY: updatebootstrap
-updatebootstrap: stage xcomp.fs
-	./stage < xcomp.fs > forth.bin
+updatebootstrap: stage1 stage1.fs
+	./stage1 < stage1.fs > forth.bin
 
 .PHONY: pack
 pack:

emul/stage.c

@@ -2,8 +2,12 @@
 #include <stdio.h>
 #include <unistd.h>
 #include "emul.h"
+#ifdef STAGE2
 #include "forth-bin.h"
 #include "blkfs-bin.h"
+#else
+#include "stage0-bin.h"
+#endif
 
 /* Staging binaries
 
@@ -70,6 +74,7 @@ static void iowr_here(uint8_t val)
     end_here |= val;
 }
 
+#ifdef STAGE2
 static void iowr_blk(uint8_t val)
 {
     blkid <<= 8;
@@ -81,6 +86,7 @@ static uint8_t iord_blkdata()
 {
     return BLKFS[blkpos++];
 }
+#endif
 
 int main(int argc, char *argv[])
 {
@@ -89,8 +95,10 @@ int main(int argc, char *argv[])
     m->iord[STDIO_PORT] = iord_stdio;
     m->iowr[STDIO_PORT] = iowr_stdio;
     m->iowr[HERE_PORT] = iowr_here;
+#ifdef STAGE2
     m->iowr[BLK_PORT] = iowr_blk;
     m->iord[BLKDATA_PORT] = iord_blkdata;
+#endif
     // initialize memory
     for (int i=0; i<sizeof(KERNEL); i++) {
         m->mem[i] = KERNEL[i];

emul/stage1.fs

@@ -0,0 +1,28 @@
+: EFS@
+    256 /MOD 3 PC! 3 PC!
+    1024 0 DO
+        4 PC@
+        BLK( I + C!
+    LOOP
+;
+: EFS!
+    256 /MOD 3 PC! 3 PC!
+    1024 0 DO
+        BLK( I + C@ 4 PC!
+    LOOP
+;
+
+: INIT
+    CURRENT @ HERE !
+    BLK$
+    ['] EFS@ BLK@* !
+    ['] EFS! BLK!* !
+    RDLN$
+    LIT< _sys [entry]
+    ." Collapse OS" NL
+;
+
+(entry) _
+H@ 0x08 BIN+ ! ( update LATEST )
+ ," INIT "
+H@ 256 /MOD 2 PC! 2 PC!

emul/xcomp.fs

@@ -9,32 +9,12 @@
 393 LOAD  ( xcomp core low )
 : (emit) 0 PC! ;
 : (key) 0 PC@ ;
-: EFS@
-    256 /MOD 3 PC! 3 PC!
-    1024 0 DO
-        4 PC@
-        BLK( I + C!
-    LOOP
-;
-: EFS!
-    256 /MOD 3 PC! 3 PC!
-    1024 0 DO
-        BLK( I + C@ 4 PC!
-    LOOP
-;
-
 420 LOAD  ( xcomp core high )
 (entry) _
 ( Update LATEST )
 PC ORG @ 8 + !
 ," CURRENT @ HERE ! "
-," : INIT "
-," BLK$ "
-," ['] EFS@ BLK@* ! "
-," ['] EFS! BLK!* ! "
-," RDLN$ "
-," LIT< _sys [entry] "
-," LIT< CollapseOS (print) NL "
-," ; INIT "
+440 446 XPACKR
+," ' (key) 12 RAM+ ! "
 ORG @ 256 /MOD 2 PC! 2 PC!
 H@ 256 /MOD 2 PC! 2 PC!

recipes/rc2014/Makefile

@@ -1,14 +1,14 @@
-TARGET = os.bin
+TARGET = stage1.bin
 BASEDIR = ../..
 FDIR = $(BASEDIR)/forth
 EDIR = $(BASEDIR)/emul
-STAGE = $(EDIR)/stage
+STAGE2 = $(EDIR)/stage2
 EMUL = $(BASEDIR)/emul/hw/rc2014/classic
 
 .PHONY: all
 all: $(TARGET) 
-$(TARGET): xcomp.fs $(STAGE)
-	cat xcomp.fs | $(STAGE) > $@
+$(TARGET): xcomp.fs $(STAGE2)
+	cat xcomp.fs | $(STAGE2) > $@
 
 $(SLATEST):
 	$(MAKE) -C $(BASEDIR)/tools

recipes/rc2014/README.md

@@ -40,7 +40,7 @@ device I use in this recipe.
 ### Gathering parts
 
 * A "classic" RC2014 with Serial I/O
-* [Forth's stage binary][stage]
+* [Forth's stage 2 binary][stage2]
 * [romwrite][romwrite] and its specified dependencies
 * [GNU screen][screen]
 * A FTDI-to-TTL cable to connect to the Serial I/O module
@@ -50,10 +50,24 @@ device I use in this recipe.
 Modules used in this build are configured through the `conf.fs` file in this
 folder. There isn't much to configure, but it's there.
 
-### Build the binary
+### Build stage 1
 
-Building the binary is as simple as running `make`. This will yield `os.bin`
-which can then be written to EEPROM.
+Self-bootstrapping is in Forth's DNA, which is really nice, but it makes
+cross-compiling a bit tricky. It's usually much easier to bootstrap a Forth
+from itself than trying to compile it from a foreign host.
+
+This makes us adopt a 2 stages strategy. A tiny core is built from a foreign
+host, and then we run that tiny core on the target machine and let it bootstrap
+itself, then write our full interpreter binary.
+
+We could have this recipe automate that 2 stage build process all automatically,
+but that would rob you of all your fun, right? Instead, we'll run that 2nd
+stage on the RC2014 itself!
+
+To build your stage 1, run `make` in this folder, this will yield `stage1.bin`.
+This will contain that tiny core and, appended to it, the Forth source code it
+needs to run to bootstrap itself. When it's finished bootstrapping, you will
+get a prompt to a full Forth interpreter.
 
 ### Emulate
 
@@ -86,9 +100,131 @@ identify the tty bound to it (in my case, `/dev/ttyUSB0`). Then:
 
     screen /dev/ttyUSB0 115200
 
-Press the reset button on the RC2014 and the "ok" prompt should appear.
+Press the reset button on the RC2014 to have Forth begin its bootstrap process.
+Note that it has to build more than half of itself from source. It takes about
+30 seconds to complete.
+
+Once bootstrapping is done you should see the Collapse OS prompt. That's a full
+Forth interpreter. You can have fun right now.
+
+However, that long boot time is kinda annoying. Moreover, that bootstrap code
+being in source form takes precious space from our 8K ROM. That brings us to
+building stage 2.
+
+### Building stage 2
+
+You're about to learn a lot about this platform and its self-bootstrapping
+nature, but its a bumpy ride. Grab something. Why not a beer?
+
+Our stage 1 prompt is the result of Forth's inner core interpreting the source
+code of the Full Forth, which was appended to the binary inner core in ROM.
+This results in a compiled dictionary, in RAM, at address 0x8000+system RAM.
+
+Wouldn't it be great if we could save that compiled binary in ROM and save the
+system the trouble of recompiling itself on boot?
+
+Unfortunately, this compiled dictionary isn't usable as-is. Offsets compiled in
+there are compiled based on a 0x8000-or-so base offset. What we need is a
+0xa00-or-so base offset, that is, something suitable to be appended to the boot
+binary, in ROM, in binary form.
+
+Fortunately, inside the compiled source is the contents of the Linker (B120)
+which will allow us to relink our compiled dictionary so that in can be
+relocated in ROM, next to our boot binary. I won't go into relinking details.
+Look at the source.  For now, let's just use it:
+
+    RLCORE
+
+That command will take the dict from `' H@` up to `CURRENT`, copy it in free
+memory and then relocate it. It will print 3 addresses during its processing.
+
+The first address is the top copied address. The process didn't touch memory
+above this point. The second address is the wordref of the last copied entry.
+The 3rd is the bottom address of the copied dict. When that last address is
+printed, the processing is over (because we don't have a `>` prompt, we don't
+have any other indicator that the process is over).
+
+### Assembling the stage 2 binary
+
+At that point, we have a fully relocated binary in memory. Depending on our
+situations, the next steps differ.
+
+* If we're on a RC2014 that has writing capabilities to permanent storage,
+  we'll want to assemble that binary directly on the RC2014 and write it to
+  permanent storage.
+* If we're on a RC2014 that doesn't have those capabilities, we'll want to dump
+  memory on our modern environment using `/tools/memdump` and then assemble that
+  binary there.
+* If we're in the emulator, we'll want to dump our memory using `CTRL+E` and
+  then assemble our stage 2 binary from that dump.
+
+In these instructions, we assume an emulated environment. I'll use actual
+offsets of an actual assembling session, but these of course are only examples.
+It is very likely that these will not be the same offsets for you.
+
+So you've pressed `CTRL+E` and you have a `memdump` file. Open it with a hex
+editor (I like `hexedit`) to have a look around and to decide what we'll extract
+from that memdump. `RLCORE` already gave you important offsets (in my case,
+`9a3c`, `99f6` and `8d60`), but although the beginning of will always be the
+same (`8d60`), the end offset depends on the situation.
+
+If you look at data between `99f6` and `9a3c`, you'll see that this data is not
+100% dictionary entry material. Some of it is buffer data allocated at
+initialization. To locate the end of a word, look for `0042`, the address for
+`EXIT`. In my case, it's at `9a1a` and it's the end of the `INIT` word.
+
+Moreover, the `INIT` routine that is in there is not quite what we want,
+because it doesn't contain the `HERE` adjustment that we find in `pre.fs`.
+We'll want to exclude it from our binary, so let's go a bit further, at `99cf`,
+ending at `99de`.
+
+So, the end of our compiled dict is actually `99de`. Alright, let's extract it:
+
+    dd if=memdump bs=1 skip=36192 count=3198 > dict.bin
+
+`36192` is `8d60` and `3198` is `99de-8d60`. This needs to be prepended by the
+boot binary. We already have `stage1.bin`, but this binary contains bootstrap
+source code we don't need any more. To strip it, we'll need to `dd` it out to
+`LATEST`, in my case `098b`:
+
+    dd if=stage1.bin bs=1 count=2443 > s1pre.bin
+
+Now we can combine our binaries:
+
+    cat s1pre.bin dict.bin > stage2.bin
+
+Is it ready to run yet? no. There are 3 adjustments we need to manually make
+using our hex editor.
+
+1. We need to link `H@` to the hook word of the boot binary. In my case, it's
+   a matter of writing `02` at `08ec` and `00` at `08ed`, `H@`'s prev field.
+2. We need to end our binary with a hook word. It can have a zero-length name
+   and the prev field needs to properly point to the previous wordref. In my
+   case, that was `RLCORE` at offset `1559` for a `stage2.bin` size of `1568`,
+   which means that I appended `0F 00 00` at the end of the file.
+3. Finally, we need to adjust `LATEST` which is at offset `08`. This needs to
+   point to the last wordref of the file, which is equal to the length of
+   `stage2.bin` because we've just added a hook word. This means that we write
+   `6B` at offset `08` and `15` at offset `09`.
+
+Now are we ready yet? ALMOST! There's one last thing we need to do: add runtime
+source. In our case, because we have a compiled dict, the only source we need
+to include is initialization code. We've stripped it from our stage1 earlier,
+we need to re-add it.
+
+Look at `xcomp.fs`. You see that `," bla bla bla"` line? That's initialization
+code. Copy it to a file like `run.fs` (without the `,"`) and build your final
+binary:
+
+    cat stage2.bin run.fs > stage2r.bin
+
+That's it! our binary is ready to run!
+
+    ../../emul/hw/rc2014/classic stage2r.bin
+
+And there you have it, a stage2 binary that you've assembled yourself.
 
 [rc2014]: https://rc2014.co.uk
 [romwrite]: https://github.com/hsoft/romwrite
-[stage]: ../../emul
+[stage2]: ../../emul
 [screen]: https://www.gnu.org/software/screen/

recipes/rc2014/eeprom/README.md

@@ -8,6 +8,7 @@ itself.
 ## Gathering parts
 
 * A RC2014 Classic
+* `stage2.bin` from the base recipe
 * An extra AT28C64B
 * 1x 40106 inverter gates
 * Proto board, RC2014 header pins, wires, IC sockets, etc.
@@ -32,21 +33,46 @@ in write protection mode, but I preferred building my own module.
 
 I don't think you need a schematic. It's really simple.
 
-### Building the binary
+### Assembling stage 3
 
-You build the binary by modifying the base recipe's `xcomp` unit. This binary
-is missing 2 things: Addressed devices and the AT28 Driver.
+Stage 2 gives you a full interpreter, but it's missing the "Addressed devices"
+module and the AT28 driver. We'll need to assemble a stage 3.
 
-Addressed devices are at B140. If you read that block, you'll see that it tells
-you to load block 142. Open the `xcomp` unit and locate the ACIA driver loading
-line. Insert your new load line after that one.
+When you'll have a system with function disk block system, you'll be able to
+directly `LOAD` them, but for this recipe, we can't assume you have, so what
+you'll have to do is to manually paste the code from the appropriate blocks.
+
+Addressed devices are at B140. To know what you have to paste, open the loader
+block (B142) and see what blocks it loads. For each of the blocks, copy/paste
+the code in your interpreter.
 
 Do the same thing with the AT28 driver (B590)
 
-You also have to modify the initialization sequence at the end of the `xcomp`
-unit to include `ADEV$`.
+If you're doing the real thing and not using the emulator, pasting so much code
+at once might freeze up the RC2014, so it is recommended that you use
+`/tools/exec` that let the other side enough time to breathe.
 
-Build again, write `os.com` to EEPROM.
+After your pasting, you'll have a compiled dict of that code in memory. You'll
+need to relocate it in the same way you did for stage 2, but instead of using
+`RLCORE`, which is a convenience word hardcoded for stage 1, we'll parametrize
+`RLDICT`, the word doing the real work.
+
+`RLDICT` takes 2 arguments, `target` and `offset`. `target` is the first word
+of your relocated dict. In our case, it's going to be `' ADEVMEM+`. `offset` is
+the offset we'll apply to every eligible word references in our dict. In our
+case, that offset is the offset of the *beginning* of the `ADEVMEM+` entry (that
+is, `' ADEVMEM+ WORD(` minus the offset of the last word (which should be a hook
+word) in the ROM binary.
+
+That offset can be conveniently fetched from code because it is the value of
+the `LATEST` constant in stable ABI, which is at offset `0x08`. Therefore, our
+offset value is:
+
+    ' ADEVMEM+ WORD( 0x08 @ -
+
+You can now run `RLDICT` and proceed with concatenation (and manual adjustments
+of course) as you did with stage 2. Don't forget to adjust `run.fs` so that it
+runs `ADEV$`.
 
 ## Writing contents to the AT28
 

recipes/rc2014/sdcard/README.md

@@ -70,23 +70,35 @@ instead.
 
 ## Building your binary
 
-The binary built in the base recipe doesn't have SDC drivers. Using the same
-instructions as in the `eeprom` recipe, you'll need to insert those drivers.
-The SDC driver is at B600. It gives you a load range. This means that what
-you need to insert in `xcomp` will look like:
+Your Collapse OS binary needs the SDC drivers which need to be inserted during
+Cross Compilation, which needs you need to recompile it from stage 1. First,
+look at B600. You'll see that it indicates a block range for the driver. That
+needs to be loaded.
+
+Open xcomp.fs from base recipe and locate acia loading. You'll insert a line
+right after that that will look like:
 
     602 616 LOADR  ( sdc )
 
-You also need to add `BLK$` to the init sequence.
+Normally, that's all you need to do. However, you have a little problem: You're
+busting the 8K ROM limit. But it's ok, you can remove the linker's XPACKing
+line: because you'll have access to the blkfs from SD card, you can load it
+from there!
+
+Removing the linker from XPACKing will free enough space for your binary to fit
+in 8K. You also have to add `BLK$` to initialization routine.
 
 Build it and write it to EEPROM.
 
+If you want, once you're all set with the SD card, you can relink core words
+like you did in the base recipe for optimal resource usage.
+
 ## Testing in the emulator
 
 The RC2014 emulator includes SDC emulation. You can attach a SD card image to
 it by invoking it with a second argument:
 
-    ../../../emul/hw/rc2014/classic os.bin ../../../emul/blkfs
+    ../../../emul/hw/rc2014/classic stage3.bin ../../../emul/blkfs
 
 You will then run with a SD card having the contents from `/blk`.
 

recipes/rc2014/selfhost/README.md

@@ -9,34 +9,24 @@ either for another RC2014 or for an OS upgrade.
 * stage3 from `sdcard` recipe. If you want to write to EEPROM as the final step,
   you'll need a hybrid stage3 that also includes stuff from the `eeprom` recipe.
 
-## Building the binary
+## Building stage 1
 
-Build Collapse OS' from within Collapse OS is very similar to how we do
+Build Collapse OS' stage 1 from within Collapse OS is very similar to how we do
 it from the makefile. If you take the time to look at the base recipe
-`Makefile`, you'll see `cat xcomp.fs | $(STAGE)`. That's the thing.  Open
-`xcomp.fs` in a text editor and take a look at it. You'll see that it loads
-B618, which contains the meat, and then spits stuff to port 2, which is a
-special signal for the `stage` binary.
+`Makefile`, you'll see `cat xcomp.fs | $(STAGE2)`. That's the thing.  Open
+`xcomp.fs` in a text editor and take a look at it.
 
-To assemble from RC2014, all you need to do is load B618. This will
-yield a binary in memory. To know the start/end offset of the binary, you'll
-type the same two commands and in `xcomp.fs`, but replace the `/MOD 2 PC! 2 PC!`
-words with `.X`. Then, write that binary between those offsets on your target
-media. That binary should be the exact same as what you get in `os.bin`
-when you run `make`.
+To assemble stage 1 from RC2014, all you need to do is to type those commands
+in the same order, and replace the `/MOD 2 PC! 2 PC!` words with `.X`.
+Those commands will inform you of the begin/end offsets of the assembled binary.
 
-Go ahead, run that. However, one thing you should know is that because the SD
-card driver is a bit slow, some of these commands take a long time. Multiple
-minutes. Be patient.
-
-Is that it? Yes. But for your own enlightenment, open B618 and look at it, I'll
-give you an overview of its contents.  I'm not going to explain in detail what
-each command do, however.  You are encouraged to read the in-system
+I'm not going to explain in detail what each command do, but only give you an
+overview of what is happening.  You are encouraged to read the in-system
 documentation for more information.
 
 The first part is configuration of your new system. When RAM starts, where RSP
-and PSP start, what ports to use for what device, etc. These configuration
-declarations are expected in the boot code and driver code.
+starts, what ports to use for what device, etc. These configuration declarations
+are expected in the boot code and driver code.
 
 Then, we load the Z80 assembler and the cross compiler (xcomp for short), which
 we'll of course need for the task ahead.
@@ -51,15 +41,41 @@ close the binary with a hook word. We're finished with cross-compiling.
 
 We're at the offset that will be `CURRENT` on boot, so we update `LATEST`.
 
-Then, we spit the init source code that will be interpreted on boot.
-And... that's it!
+Then, we spit the source code that will be interpreted by stage 1 on boot so
+that it bootstraps itself to a full interpreter. Not all units are there
+because they don't fit in 8K, but they're sufficient for our needs. We also
+need the linker so that we can relink ourselves to stage 2.
+
+Finally, we have initialization code, then a spit of the ending offset.
+
+Go ahead, run that. However, one thing you should know is that because the SD
+card driver is a bit slow, some of these commands take a long time. Multiple
+minutes. Be patient.
+
+Once all your commands are run and that you have your begin/end offset (write
+them down somewhere), you're at the same point as you were after the `make`
+part of the base recipe. The contents between your start and end offset is the
+exact same as the contents of `stage1.bin` when you run `make`. Continue your
+deployment from there.
+
+Good luck!
 
 ### What to do on SDerr?
 
 If you get `SDerr` in the middle of a LOAD operation, something went wrong with
 the SD card. The bad news is that it left your xcomp operation in an
-inconsistent state. The easiest thing to do it to restart the operation from
-scratch. Those error are not frequent unless hardware is faulty.
+inconsistent state. If your at the beginning of it, it's easier to restart it
+entirely.
+
+If you're towards the end, you might want to repair it. To do so, you'll have to
+bring your `XCURRENT` and `HERE` values to where they were before the LOAD
+operation. You could have thought ahead and printed them before the LOAD, but if
+you didn't, you'll just have to dig in your memory with `DUMP`.
+
+You're looking at the offset of the last wordref of the *previous* LOAD
+operation. That offset is going in `XCURRENT`. Then, you're looking at the end
+of that word. That offset goes in `HERE`. Once you've done that, relaunch your
+LOAD.
 
 ### Verifying
 

recipes/rc2014/xcomp.fs

@@ -1,3 +1,25 @@
-618 LOAD
+0x8000 CONSTANT RAMSTART
+0xf000 CONSTANT RS_ADDR
+0xfffa CONSTANT PS_ADDR
+0x80   CONSTANT ACIA_CTL
+0x81   CONSTANT ACIA_IO
+4      CONSTANT SDC_SPI
+5      CONSTANT SDC_CSLOW
+6      CONSTANT SDC_CSHIGH
+RAMSTART 0x70 + CONSTANT ACIA_MEM
+212 LOAD  ( z80 assembler )
+262 LOAD  ( xcomp )
+270 LOAD  ( xcomp overrides )
+
+282 LOAD  ( boot.z80 )
+393 LOAD  ( xcomp core low )
+582 LOAD  ( acia )
+420 LOAD  ( xcomp core high )
+(entry) _
+( Update LATEST )
+PC ORG @ 8 + !
+440 446 XPACKR ( core )
+123 132 XPACKR ( linker )
+," : _ ACIA$ RDLN$ (ok) ; _ "
 ORG @ 256 /MOD 2 PC! 2 PC!
 H@ 256 /MOD 2 PC! 2 PC!

recipes/ti84/Makefile

@@ -1,15 +1,15 @@
-TARGET = os.bin
+TARGET = stage1.bin
 BASEDIR = ../..
 FDIR = $(BASEDIR)/forth
 EDIR = $(BASEDIR)/emul
-STAGE = $(EDIR)/stage
+STAGE2 = $(EDIR)/stage2
 EMUL = $(BASEDIR)/emul/hw/ti/ti84
 MKTIUPGRADE = mktiupgrade
 
 .PHONY: all
 all: $(TARGET) 
-$(TARGET): xcomp.fs $(STAGE)
-	cat xcomp.fs | $(STAGE) > $@
+$(TARGET): xcomp.fs $(STAGE2)
+	cat xcomp.fs | $(STAGE2) > $@
 
 $(EMUL):
 	$(MAKE) -C ${@:%/ti84=%}

recipes/ti84/README.md

@@ -38,7 +38,7 @@ screen as output and its builtin keyboard as input.
 
 ## Build the ROM
 
-Running `make` will result in `os.rom` being created.
+Running `make` will result in `stage1.rom` being created.
 
 ## Emulate
 

recipes/ti84/xcomp.fs

@@ -68,6 +68,7 @@ CREATE ~FNT CPFNT3x5
 (entry) _
 ( Update LATEST )
 PC ORG @ 8 + !
+440 446 XPACKR ( core )
 ," : _ LCD$ KBD$ (ok) RDLN$ ; _ "
 ORG @ 0x100 - 256 /MOD 2 PC! 2 PC!
 H@ 256 /MOD 2 PC! 2 PC!

recipes/trs80/Makefile

@@ -1,8 +1,8 @@
-TARGET = os.bin
+TARGET = stage1.bin
 EDIR = ../../emul
-STAGE = $(EDIR)/stage
+STAGE2 = $(EDIR)/stage2
 
 .PHONY: all
 all: $(TARGET) 
-$(TARGET): xcomp.fs $(STAGE)
-	cat xcomp.fs | $(STAGE) > $@
+$(TARGET): xcomp.fs $(STAGE2)
+	cat xcomp.fs | $(STAGE2) > $@

recipes/trs80/README.md

@@ -67,10 +67,10 @@ kind of reception! You're gonna feel real badass about it too...
 
 * `_` is `CLEAR+ENTER`.
 
-## Building the binary
+## Building the stage 1
 
-You can build the binary to send to the TRS-80 with `make`, which will yield
-`os.bin`. You'll need it later.
+You can start the process by building the stage 1 binary. Running `make` in
+this folder will yield a `stage1.bin` file. You'll need it later.
 
 ## Testing serial communication
 

recipes/trs80/xcomp.fs

@@ -7,13 +7,15 @@ RS_ADDR 0x80 - CONSTANT RAMSTART
 
 0x3000 BIN( !
 282 LOAD  ( boot.z80 )
+492 LOAD  ( trs80.z80 )
 393 LOAD  ( xcomp core low )
-492 LOAD  ( trs80 )
 420 LOAD  ( xcomp core high )
 (entry) _
 ( Update LATEST )
 PC ORG @ 8 + !
 ," CURRENT @ HERE ! "
+440 446 XPACKR ( core )
+499 500 XPACKR ( trs80.fs )
 ( 0x0a == NLPTR. TRS-80 wants CR-only newlines )
 ," : _ ['] CR 0x0a RAM+ ! BLK$ FD$ (ok) RDLN$ ; _ "
 ORG @ 256 /MOD 2 PC! 2 PC!

tests/forth/test_sdc.fs

@@ -2,7 +2,8 @@
 : SDC_SPI 4 ;
 : SDC_CSLOW 5 ;
 : SDC_CSHIGH 6 ;
-602 616 LOADR ( sdc )
+372 LOAD ( sdc.z80 )
+374 LOAD ( sdc.fs )
 
 0x0000 0x00 _crc16 0x0000 #eq
 0x0000 0x01 _crc16 0x1021 #eq