Problem NMS-8245 2+, black screen

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By Caliostro

Expert (74)

Caliostro's picture

14-06-2021, 17:38

i am building an expansion with 2 4464, where should i connect CAS-RAS?

By lintweaker

Champion (407)

lintweaker's picture

14-06-2021, 19:43

Caliostro wrote:

i am building an expansion with 2 4464, where should i connect CAS-RAS?

/RAS and /CAS need a bit of circuitry. You can check existing designs for an example.
Do you have access to SRAM ICs? They are a bit easier as they do not need to be refreshed.

By Caliostro

Expert (74)

Caliostro's picture

14-06-2021, 20:06

can i use this?
[img][/img]

By Pentarou

Champion (376)

Pentarou's picture

14-06-2021, 21:15

Where does that come from? Was the 8245 expanded to 1MB?

By Caliostro

Expert (74)

Caliostro's picture

14-06-2021, 21:49

yes, a 1MB expansion was mounted, I disassembled it and restored the ram as original

By Jipe

Paragon (1489)

Jipe's picture

15-06-2021, 08:16

for expand 8245 to 1MB required a mini mapper
see Hans Oranje pagina search NMS8245 : https://www.hansoranje.nl/
have you it on your MSX ?

By Caliostro

Expert (74)

Caliostro's picture

15-06-2021, 10:24

yes,
[img][/img]
but that's not what I want to do, can I only use part of that ram to make a simple 64k expansion cartridge?

By Jipe

Paragon (1489)

Jipe's picture

15-06-2021, 10:44

the SIMM 1MB is DRAM dynamic ram and required refresh circuit

use a SRAM for making a 64k expansion cartridge is more simple

for testing with original RAM
have you 2x 81464 DRAM ( 64k x 4bits ) ?
remove the circuit with SIMM
plug the 81464 on U3 and U4
the MSX start with 64k ram inside Smile

you can make a 64k extension with 2 x 43256 SRAM, 1 x HCT32 and 1 x HCT00
http://msxvillage.fr/forum/topic.php?id=766&pt=1
see the third schematic

By Jipe

Paragon (1489)

Jipe's picture

15-06-2021, 11:02

your circuit is not the mini-mapper of Hans Oranje but other extension
try the mini-mapper + /cas select , it work fine and more simple

i find a link in english Wink
https://manualzz.com/doc/19765703/how-to-build-1-mb-simm-in-...

By Caliostro

Expert (74)

Caliostro's picture

15-06-2021, 15:35

Anyway, I have to order something .... thank you very much for all these tips, I'll be back when I have the material for the cartridge, now I have to stop the repair

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