hpr4022 :: dumping roms for fun and profit
using forth to do something useful
Hosted by Brian in Ohio on 2024-01-02 is flagged as Clean and is released under a CC-BY-SA license.
z80, retro computing, forth.
1.
The show is available on the Internet Archive at: https://archive.org/details/hpr4022
Listen in ogg,
spx,
or mp3 format. Play now:
Duration: 00:17:19
general.
disassembling - hex2bin is used for converting hexadecimal files into a binary file. - used z80dasm to disassemble machine code into hexadecimal - use xxd to view the hex code and machine code side by side - ghidra, reverse engineering suite used for analysis
https://www.noagendashow.net/ https://twostopbits.com/ https://en.wikipedia.org/wiki/Programmable_ROM https://en.wikipedia.org/wiki/Dual_in-line_package https://www.tablix.org/~avian/blog/articles/z80dasm/ https://ghidra-sre.org/ https://hex2bin.sourceforge.net/
1.prom-location-on-board.jpg 2.prom-ready-to-read.jpg
Intelhex file snipet:
:100600003E0FCD8E043E0ECD8E04211441360023C4
:1006100036003A6341326A41CDB204CDC404CD61A3
:1006200005215541CB46C46306210F41CB6E281CE2
:10063000210241CB4E28CE210F41CB7E2809FEEC72
:10064000CAC306FEED287CCD45071849CB66284570
:10065000210741CB76203B21154134CB8ECB9ECB5D
:10066000961832FEFFC8CB4E2808FEE42004CB8E3D
:10067000D1C9211941BED0FE31D8215541CB6628C0
:1006800003FE31C8321341CBA7CBAF215541CBD6A6
:10069000D1C9CD45072114413400003A2E41BEC2D4
:1006A0001E0636000000211541CB46216B417E2BF2
:1006B0002016BE200F3E132B772124413600210F38
:1006C000413EFFC934C31806BE28EA3EC9CD8E0498
:1006D0002115417EC60477CB5E200CCBA6AF01006E
:1006E00041CD9104C31E063E2018F3210F41CB6675
:1006F000202DCB6E28093A1341FEE4CCD107C93E28
:10070000FFC9CDEB06210F41CB662013CB6E28EF3E
:100710003A1341FEE12804FEE22004CDD107C93A94
:100720001341C93E200614219042772310FCC921B1
:100730002541367C233614CD5207C9212541362068
:1007400023362018F2FB2125413680233601CD5374
:1007500007C9F31680211241CBCECB964E0640CB73xxd output showing text that's displayed on the screen when the device boots
000025d0: f4f5 f6f7 f9ef e1e2 0ded e8f8 30e4 3d3b ............0.=;
000025e0: 272f e550 3839 4f4b 4c2c 2e49 3637 5548 '/.P89OKL,.I67UH
000025f0: 4a4e 4d59 3435 5446 4756 4252 3233 4553 JNMY45TFGVBR23ES
00002600: 4458 4357 e631 5141 5ae7 20ec ebea 2020 DXCW.1QAZ. ...
00002610: 2020 2020 0f53 454c 4543 5420 4143 5449 .SELECT ACTI
00002620: 5649 5459 1053 454c 4543 5420 434c 4153 VITY.SELECT CLAS
00002630: 5320 312d 3906 4c45 5353 4f4e 1053 454c S 1-9.LESSON.SEL
00002640: 4543 5420 4c45 5645 4c20 312d 3405 4c45 ECT LEVEL 1-4.LE
00002650: 5645 4c12 5345 4c45 4354 2053 4543 5449 VEL.SELECT SECTI
00002660: 4f4e 2031 2d32 1231 2d45 5841 4d50 4c45 ON 1-2.1-EXAMPLE
00002670: 2050 524f 4752 414d 5310 322d 4241 5349 PROGRAMS.2-BASI
00002680: 4320 434f 4d50 5554 4552 1045 5841 4d50 C COMPUTER.EXAMP
00002690: 4c45 2050 524f 4752 414d 530e 5052 452d LE PROGRAMS.PRE-
000026a0: 4241 5349 4320 5631 2e30 1253 454c 4543 BASIC V1.0.SELECz80dasm output:
push af ;0040 f5 .
push bc ;0041 c5 .
push de ;0042 d5 .
push hl ;0043 e5 .
ld hl,0410fh ;0044 21 0f 41 ! . A
res 4,(hl) ;0047 cb a6 . .
res 5,(hl) ;0049 cb ae . .
set 6,(hl) ;004b cb f6 . .
bit 0,(hl) ;004d cb 46 . F
jr nz,27 ;004f 20 19 .
bit 1,(hl) ;0051 cb 4e . N
jr z,41 ;0053 28 27 ( '
ld hl,0410eh ;0055 21 0e 41 ! . A
inc (hl) ;0058 34 4
ld a,(hl) ;0059 7e ~
cp 032h ;005a fe 32 . 2
jr nz,32 ;005c 20 1e .
ld (hl),000h ;005e 36 00 6 .
ld hl,0410ch ;0060 21 0c 41 ! . A
inc (hl) ;0063 34 4
jr nz,24 ;0064 20 16 .
inc hl ;0066 23 #
inc (hl) ;0067 34 4
jr 20 ;0068 18 12 . .
ld hl,0410ch ;006a 21 0c 41 ! . A
inc (hl) ;006d 34 4
jr nz,14 ;006e 20 0c .
inc hl ;0070 23 #
inc (hl) ;0071 34 4
ld a,(hl) ;0072 7e ~
cp 00ch ;0073 fe 0c . .
jr nz,7 ;0075 20 05 .
ld hl,0410fh ;0077 21 0f 41 ! . A
set 2,(hl) ;007a cb d6 . .If you've gotten this far, the forth code, read bottom up:
-promreader
marker -promreader
2variable low-mem
2variable high-mem
\ 22-29
$22 constant LOW-BYTE
$21 constant DDRA
$20 constant PINA
\ 53=PB0, 52=PB1
$25 constant PAGE
$24 constant DDRB
$23 constant PINB
%0000.0001 constant PAGE-SELECT
%0000.0010 constant CHIP-ENABLE
\ 37-30 (reversed on board)
$28 constant HIGH-BYTE
$27 constant DDRC
$26 constant PINC
\ 49-42 (reversed on board)
$10b constant PORTL
$10a constant DDRL
$109 constant DATA
variable LineFeed
variable Address
variable CheckSum
$10 constant ByteCount
0 constant RecordType
: port-init ( -- )
PAGE-SELECT DDRB mset
CHIP-ENABLE DDRB mset
$ff DDRA mset
$ff DDRC mset
$ff DDRL mclr
$ff PORTL mset
CHIP-ENABLE PAGE mset
PAGE-SELECT PAGE mclr
;
: hex>ascii ( n -- c c ) dup $f0 and 4 rshift swap $0f and digit swap digit ;
: checksum+ ( n -- ) CheckSum @ + CheckSum ! ;
: .output ( n -- ) ( dup ) ( checksum+ ) emit emit ;
: address ( n -- )
Address @
dup $ff00 and 8 rshift swap
$00ff and swap
dup checksum+
hex>ascii
.output
hex>ascii
.output
;
: add>bytes ( n -- n n ) dup $ff00 and 8 rshift swap $00ff and ;
: build-record ( n -- ) dup checksum+ hex>ascii .output ;
: header ( -- )
." :"
ByteCount build-record
Address @ add>bytes swap build-record build-record
RecordType build-record
;
: .checksum ( -- )
CheckSum @ invert 1+
build-record
0 CheckSum !
cr
;
: address+ ( -- n ) Address @ 1+ dup Address ! ;
: line-feed+ ( -- )
LineFeed @ 1+
dup
ByteCount = if
( .checksum )
0 LineFeed !
cr
else
LineFeed !
then
;
: read-data ( -- d )
CHIP-ENABLE PAGE mclr 10 ms
DATA c@ 10 ms
CHIP-ENABLE PAGE mset 10 ms
;
: set-high-byte HIGH-BYTE c! ;
: set-low-byte LOW-BYTE c! ;
: get-data ( -- n )
Address @ add>bytes
set-low-byte
set-high-byte
read-data
build-record
;
: page-read ( -- )
0 CheckSum ! 0 Address ! cr
begin
0
header
begin
get-data
Address @ 1+ Address !
1+
dup 16 =
until
drop
.checksum
Address @
0=
until
." :00000001FF" cr
;
: dump-prom ( -- )
port-init
." Page 1" cr
page-read
PAGE-SELECT PAGE mset
." Page 2" cr
page-read
;PROM location on board
PROM ready to read
