Programming nms8245 eprom

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By spacegremlin

Expert (80)

spacegremlin's picture

20-02-2016, 20:08

hello i am trying to program a eprom for the nms8245.

i have a pc programmer for eproms.
i have several eproms cleared ready for programming.
the eprom i use is 27c512.
when it is programmed the msx does not startup.
i used several rom files from the net wich would be good for in the eprom.
but no luck.

what i want to no what am i doing wrong. and i use 27c512 instead of the 27512 is that a problem.

programmer i use :
MiniPro TL866cs EEPROM Programmer,
thank you.

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By Jipe

Paragon (1499)

Jipe's picture

20-02-2016, 20:45

the original eprom is a 128K
on 8245 exist a strap for choise the 64k bank by the A16 bit
search JP1 JP2 on the main board and invert the config

By spacegremlin

Expert (80)

spacegremlin's picture

20-02-2016, 20:50

okey , so if use a 128k it should work, then i first try to program a 27c128. i have them also.

i see i do not have, only 256 and 512 so i will check the jp settings you say

By spacegremlin

Expert (80)

spacegremlin's picture

20-02-2016, 21:30

i checked the schematic. jp2 is now connected with a resistor. so we remove the resistor and connect it on the jp1.

it looks like, now its a pullup. and it goes to a pulldown. lets see what that does.

By RetroTechie

Paragon (1563)

RetroTechie's picture

21-02-2016, 02:58

spacegremlin wrote:

okey , so if use a 128k it should work, then i first try to program a 27c128. i have them also.

i see i do not have, only 256 and 512 so i will check the jp settings you say

27C128 = 16 KB. 27C256 = 32 KB. Both no good.

27(C)512 should be a plug-in replacement for the 1 Mbit ROM in an NMS8245. But you have to make sure that both pins 20 and 22 are pulled low when active, not wired to +5V. That means jumper in JP1 position. And on pin 20 the schematic shows another one (ST1), that should be in 1-2 position (across R97).

The other issue is what file you're using & how blocks within the 64 KB are arranged. Make sure 16 KB blocks within the EPROM are ordered as follows:

Block Contents
0 BIOS (0000-3FFFh contents)
1 BIOS/BASIC (4000-7FFFh contents)
2 MSX2 subROM
3 diskROM

By Jipe

Paragon (1499)

Jipe's picture

21-02-2016, 11:44

the jp1 jp2 is for choise the 64k bank in the 128K rom ( choise by A16 pin 22)
see the schematic note : 1 present in /00 , 2 present in /16
with a 27C512 the pin 22 is /OE VPP and the strap on JP1 for active the /OE signal

By spacegremlin

Expert (80)

spacegremlin's picture

21-02-2016, 13:08

so if correct.
see picture.

jp1 goes on ground.
jp2 remove resistor
r97 has a jumper setting beside it. set it to 1-2 , for me thats already that way.

am i correct?

then i only have to see how to make the rom.
i also understand when this has been done, the original rom will nog work anymore?

i want to do the v9958 upgrade, can i do the bios msx2+ upgrade first to see it work, and then the vdp chip.
or will the msx2+ bios not work without the vdp9958. because then i had the idea to first upgrade the 27c512 chip.
set with the nms8245 bios to see it work with the standard vdp chip

1 other question, standaard the rom is 1Mbit why isnt there a 1mbit eprom used? and i assume there is only be used less then 512kb in the rom?

By spacegremlin

Expert (80)

spacegremlin's picture

21-02-2016, 13:42

how do i get the nms8245 complete rom
and the msx2+ complete rom for the nms8245.

i cannot find the correct files, and i have many.

By RetroTechie

Paragon (1563)

RetroTechie's picture

21-02-2016, 13:56

MSX2+ basic allows you to set screen modes >8 that aren't supported by a V9938. OTOH, a V9958 supports all screen modes that a V9938 does. In other words: upgrading VDP first, and ROMs later is the safer route. Also some software can use a V9958 even without 2+ ROMs.

spacegremlin wrote:

standaard the rom is 1Mbit why isnt there a 1mbit eprom used?

The NMS8245 only uses 64 KB (512 kbit) ROM. Philips just put in a 2x that size ROM with a jumper to select which half is used. I suspect for different country settings or whatever. Maybe using the same 1 Mbit ROM + jumper was cheaper / simpler than keeping different ROMs in stock & swapping those.

As for the 2+ ROMs to use: I suggest you try on emulator first to determine the ROMs satisfy your needs. Rather than wasting time on burning EPROM, put in & then find out something's not working right. Correct ROMs to use also depend on whether you implement F4 register or not, and if so, how. And whether you want to keep that 2+ boot logo on board or cut it out. Again: check with emulator first.

By spacegremlin

Expert (80)

spacegremlin's picture

21-02-2016, 14:08

clear.

i will do. but for the roms i do not get.
i check the emulator, for the set that works. i did that also. but then i have like.

disk.rom
msx2p.rom
and maybey i need more i do not know.

but how do i get these to roms burnt in my eprom at ones.
if i like load the first rom in the program, and then the second one in the program, clears the program and loads the second rom.
so they are not both in the program.
Hope you understand what i mean.

I did eprom programming before, and had no problems, until now to get the system rom correct.

i also understand the rom is not needed, but msx2+ or not, maybe i want to upgrade the diskrom.
and even that i cant get to work.

greetings.

By Jipe

Paragon (1499)

Jipe's picture

21-02-2016, 16:12

see the 2 last post for eproms 2+ on 8235/39 model and picture of 64k + 16k eprom
and 2 first post in next page for some detail
http://www.msxvillage.fr/forum/topic.php?id=475&pt=2

the schematic of the 8245 and 8235/39 are very similary

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