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Development history of SamForth disassembled

2012-12-22

Version A-00 of SamForth2z80dasm. First tries to automatically create the data files needed by the disassembler. Symbols for word headers.

2012-12-23

Versions A-01 and A-02 of SamForth2z80dasm. New better method. Symbols for word headers. Symbols for system variables.

2012-12-26

Version A-03 of SamForth2z80dasm. Symbols for RST addresses and their vectors. Symbol for some discovered routines.

2012-12-27

The original code is STC (Subroutine Threaded Code), not DTC (Direct Threaded Code) as I wrote at first.

The following commands from the definition of VLIST reveal that six bits are used for the word name length:

  ld c,(hl)  ;15ba
  res 7,c    ;15bb
  res 6,c    ;15bd

That means SamForth words can be 63 characters long.

2012-12-28

The dissasambled code was assembled back by the first time, with pyz80 and Pasmo. In the first case, the hexadecimal numbers format must be changed first (from the "h" suffix to the "&" prefix). The resulting code run perfectly.

New discoverings:

At 00C0h there is a jump table that holds many ROM addresses.

RST 8 calls ROM's RST 10: prints char in A to current stream.

RST 10 pushes HL.

RST 18 pops HL.

RST 20 pushes HL and DE.

RST 28 pops HL and DE.

RST 30 reports the error whose number is in A; the error messages are in stored in the zone 10E1H - 117BH.

The routine at l117ch does the init.

The routine at sub_1085h prints a string (start in HL, count in BC).

The routine at l0e9dh accepts keyboard input.

The routine at sub_1525h gets the next word from the input stream; it's used by variable, create, :, builds, constant...

The routine at sub_11a9h saves HERE and LATEST variables; It's used by ;, and at the end of create, c,, ,, allot, ;code, variable, constant.

The routine at sub_11b6h restores HERE and LATEST variables, sets STATE to 0. This is the last routine before the dictionary.

In jr nz,l11c7h ;115f ret nz can be used instead. There are several minor improvementes like this one.

Words with the precedence bit (7th bit of the name length byte) set: :, ;, ;code, code:, cold, ascii.

Words with the 8th bit of the name length byte set: do, +loop, loop, .", begin, until, if, else, endif, then, builds, does, while, repeat. That means the 8th bit is the "compile-state-only" bit!

The value of STATE is 0 or 80h, as the following piece of code shows (there are more examples):

code_colon_cfa:
  ld a,080h       ;16ab
  ld (STATE),a    ;16ad

2012-12-29

Version A-04 of SamForth2z80dasm, with support for SamForth-B. SamForth-B disassembled.

2013-01-01

Start and exit routines disassembled. They are poked at 50000 and 50020 by the the BASIC loaders. Also the routine loaded by SamForth-A at 50040 has been disassembled.

2013-01-04

SamForth2z80dasm improved:

• Several new routines marked.
• Symbols file indentation fixed: it failed with labels exactly 30 chars long.

z80dasm2tidySamForth improved:

• Typo fixed.
• Headers finished.
• Bug fixed: the defb->defw byte order was wrong.
• The _name: symbols are not removed anymore, because they are needed to translate the links.
• The symbols of JVSIN's arguments are removed.
• The link field addresses are converted to their corresponding symbols.
• Symbols for SAM's memory page registers.
• Some special cases fixed in the assembly.
• Word names are converted to defm.

2013-01-05

SamForth2z80dasm improved:

• Many new routines marked with symbols.

z80dasm2tidySamForth improved:

• Code divided into functions.
• New functions to add comments to the final source.
• Error messages are converted to defm.
• Special cases fixed.

2013-01-06

SamForth2z80dasm improved:

• Return stack marked.

z80dasm2tidySamForth improved:

• All ROM routines are translated to symbols.
• All SamForth variables are commented with the descriptions found in the original documentation.
• All data zones (tib, pad and stacks) are converted to defs.

2013-01-07

SamForth2z80dasm improved:

• Fixed the address of cls in SamForth-A.
• Several new routines marked.
• New symbols.

z80dasm2tidySamForth improved:

• Finished the comments of ROM routines.
• The contents of SamForth's variables are converted to symbols if needed.
• Every variant now defines only the required << abbr ROM />> routines.

2013-01-08

SamForth2z80dasm improved:

• Two nop unknown zones in SamForth-B are marked in order to convert them to defs during the postprocessing.
• Symbol for 0x0066 (the NMI routine), needed in SamForth-A.

z80dasm2tidySamForth improved:

• Two nop unknown zones in SamForth-B, marked during the preprocessing,
• are converted to defs.
• All padding nop above the rst addresses are removed; an org is put instead.
• The format of the rst values is changed with the prefered hex prefix.

2013-01-20/23

Several improvements, mainly new routines understood and labelled while working on ForthCoupe.

2013-01-20

z80dasm2tidySamForth improved:

• Now double quotes are used to surround defm strings; single quotes are accepted by Pasmo but not by pyz80.
• Type fixed in Z80Comments.
• The notation of the ." word name is changed to be compatible with both pyz80 and Pasmo.

2013-01-21

SamForth2z80dasm improved:

• Fix: jp_u_dot_header_end renamed to jp_u_dot_code_field.
• Fix: the call_rom_address_in_iy symbol was not defined in SamForth-B. The routine exits, but it's not used.
• New symbols: compile_call_tos, compile_call_de, error_0x01_stack_empty, error_0x02_stack_full, call_push_hl, return_from_basic.
• New symbols of the keybord input routine.

z80dasm2tidySamForth improved:

• New comments, on an useless ret after a jp.
• New comments, on an useless jp jp_link_l after a jp jp_link.
• New comment in SamForth-B, on the useless call_rom_address_in_iy routine (a remain from SamForth-A).
• New comments on sub_49e2h (SamForth-B) and sub_0aaeh (SamForth-A).
• New comments on useless pop de before udgdef:.
• Fixed comment: tempstk_fvar is used by SamForth-B.
• Removed comments on the words that return the address of stack manipulation code in SamForth-B (e.g. push-hl).
• Fixed: regex that removes the first definition of jsvin_rom_routine.
• New comment on the new return_from_basic label.
• New comments on the l59bah label in SamForth-B.
• New comment on the new print_cr label.
• New comments on the usage of tempstk_fvar in udgdef.

2013-01-22

SamForth2z80dasm improved:

New: block zones for all 0branch.

z80dasm2tidySamForth improved:

• New comment on corestore_fvar.
• New: Z80BranchsToSymbols().

2013-01-23

SamForth2z80dasm improved:

New names for unknown symbols: toggle_caps_lock, toggle_insert_mode.

Related pages

SamForth disassembled

Disassembling of SamForth.

SamForth documentation

Edited documentation of SamForth, a Forth system for the SAM Coupé computer.

SamForth2z80dasm

Tool program to disassemble SamForth.