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

:1007500007C9F31680211241CBCECB964E0640CB73

xxd 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.SELEC

z80dasm 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 .