NEOS MA-20 clone (read inside)

By l_oliveira

Hero (534)

23-01-2014, 20:20

Here is my VG-8020-00 running with the kit. There is a ESE-SCC cartridge on slot1, the cloned kit on slot 2.

Closer look at the cloned kit connected to a CIEL slot expander:

The insides of the modified CT-80 NET cartridge:

The other side:

Snake ?! Snaaaaaaaake !!!

Just like the original, the kit consists of two cartridges, one being the VDP(@ IO port 88h) and SUB-ROM the other being the MAIN-ROM and real time clock chip. Since it has no RTC circuit yet, I had to hack the SUB-ROM so it would skip RTC init. B-)

I'd like to thank the folks at openMSX for supporting this device on their fine emulator, resulting on the ROMs being publicly available.

By AxelF

Champion (398)

23-01-2014, 22:59

And where CAN we download these publicly available ROM's ?

By mars2000you

Enlighted (6557)

23-01-2014, 23:09

Here (posted by fabf in another thread) :

http://fabf38.free.fr/diy/ma20/ma20.rar

By AxelF

Champion (398)

23-01-2014, 23:11

mars2000you wrote:

Here (posted by fabf in another thread) :

http://fabf38.free.fr/diy/ma20/ma20.rar

Thanx ;)

By JINsMac

Expert (77)

24-01-2014, 02:27

good work~

By hbarcellos

Hero (649)

11-03-2014, 17:17

AFAIK, this is how to convert the ROMS and SUBROMS (friend of mine sent those):
*PS* Sorry for the Portuguese.

******************************
********************************************************
* By Muffie - 05/06/2009
* #PS# Não é uma publicação científica, ou seja, não espere muita
formalidade...
*************************************************************************************

1) primeiro tem que debugar a ROM/SUBROM para ver o que tenta ler e/ou
escrever nas portas do RTC ($b4 e $b5)
2) Identificadas algumas funções na subrom:
$ 1c60 - lê o registro do clock indicado por "B" e retorna em
"A" (os valores são todos de 4 bits). Não muda o modo/página do RTC.
pega o registro do modo corrente.
$ 1c81 - Seta Modo 3
$ 1c85 - Seta Modo 2
...
3) Para encurtar caminho emulei a maquina no openMSX e arranquei fora
a emulação de RTC (editando o hardwareconfig.xml)

phc-70fd2.cmos

$ -->

4) Quando a emulação fica em loop, basta identificar onde estava
travando.
5) Na subrom $044a tinha uma chamada assim: "044a cd691c call
#1c69", onde ia ler um valor do RTC.
6) Para encurtar o caminho ainda mais, re-emulei o RTC e coloquei um
breakpoint aí pra ver qual valor era esperado com o rtc presente: $1D
7) Então foi só trocar os bytes "cd 69 1c" por "00 3e 1d", ou seja:
LD A,$1D

- Pronto, a máquina boota, mas... A tela fica toda branca. Um color
1,11,11 arruma a cor, mas o posicionamento dos caracteres e o width
estão super estranhos.

8) Achei as seguintes funções na subrom:

Address : #0185
Function : Recovers screen-parameters of clock-chip. When C-flag is
set

Address : #0189
Function : Recovers screen-parameter and prints Welcome message

9) Na subrom estes endereços tem:
...
0185 fb ei
0186 c3fc04 jp #04fc
0189 fb ei
018a c3d604 jp #04d6
...

então foi só trocar: "c3 fc 04" por "00 00 c9" => "nop nop ret"
e "c3 d6 04" por "00 00 c9" também

Pronto, inicia direitinho...

By Lord_Zett

Paladin (807)

28-06-2017, 19:32

is there more info about the neos clone? or can we buy them?

By zeilemaker54

Champion (355)

29-06-2017, 03:44

Generated source code is available (and easy configureable with other country settings) in my msxsyssrc project. You can generate your own roms with it.
https://sourceforge.net/p/msxsyssrc/git/ci/master/tree/special/ma-20/

By PingPong

Enlighted (4155)

30-06-2017, 14:34

Good configuration expecially suited for easy keyboaard typing

By djh1697

Paragon (1736)

02-07-2017, 00:34

I wonder if the bright guys at 8bits could do an MSX2 or even an MSX2+ FPGA implementation? Would be a wonderful upgrade for an MSX1! Back to reality, there probably isn't enough space on the chip