Slot and Memory mapper on SVI 738 DIY to MSX2/MSX2+

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By lkpalwa

Expert (92)

lkpalwa's picture

08-04-2019, 11:34

Have now successfully a embryo to a mapper, but next question before I plug in and start testing
Default memory is put on SLOT1 and Cartigde on SLOT2, recommend fix I have seen on MSX docs are move memory
to SLOT2 and Cartidge to SLOT1 or should I complex things and move RAM to SLOT3-X
What is the best option to make it compatible with MSX2/MSX2+ standard.
Internal Memorymapper is of 256KB using default design from DATA PAC docs + some additional glue logic Smile
Looking at most MSX2/2+ it looks like slot 3 is more popular, but then I need to move disk rom/RS232 Sad

Any help appricated Tongue Tongue Tongue

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By NYYRIKKI

Enlighted (5382)

NYYRIKKI's picture

08-04-2019, 12:24

Indeed RAM in slot 3-x is a good idea. I think 3-0 and 3-2 are clearly the most popular choices around. How ever please note that 738 slot 3-x signals are not quite complete and lack the #C000-#FFFF area, so it is not quite as simple as swapping the signals, but naturally can be done with some extra glue logic... Personally I've not investigated this possibility ATM.

Ps. The RS-232 ROM is a bit problematic as the variables conflict a bit with other things on MSX2 and up.

By msxholder

Champion (336)

msxholder's picture

08-04-2019, 12:32

The secondary slot select register is several times mirrored in page 3 and 4,some more adressing logic is needed.
if you move the Ram to an other slot as 1 it would not boot CP/M any more.

By lkpalwa

Expert (92)

lkpalwa's picture

08-04-2019, 12:44

hmm, but if you look at SVI Tech PDF - sheet (memory decoder) Tongue
the IC63 give SLt30 to SLT33 (LS139) and RS232 and DISCROM additonal NAND and address if handle by the 8 NAND (IC61) + Inverter for example the diskrom ? Or I am doing wrong reading schematics Sad

By lkpalwa

Expert (92)

lkpalwa's picture

08-04-2019, 13:08

SLT1 singal is connected direct to RAMSLECT and SLT2 is used to Cartidge - SLT2 signal is not used in any other part in schematics Smile as I can see

By lkpalwa

Expert (92)

lkpalwa's picture

08-04-2019, 13:09

CP/M I think can be hacked to work, I think I have seen some docs on that, to make it work on MSX2 and MSX2+

By lkpalwa

Expert (92)

lkpalwa's picture

08-04-2019, 13:29

I think the IC41 LS133 is used for decoding the SL31 and put the DISKROM on SL31 4000H-7FFFH
Nyyrikki thx for the help with MSX2+ upgrade last year Wink , now I try to solve the memory map issue now Crazy

By NYYRIKKI

Enlighted (5382)

NYYRIKKI's picture

08-04-2019, 17:42

Usually at this point I browse quickly in to Hans Otten pages to reply something vice... Now I don't... and it is not your fault.
... but generally what you say sounds right to me.

By lkpalwa

Expert (92)

lkpalwa's picture

08-04-2019, 18:10

Yes I know I sad that he have left the MSX community oO oO oO

By gdx

Prophet (3030)

gdx's picture

09-04-2019, 02:46

The easiest way for the SVI-738 is to reverse the signal /SLTSL of internal RAM with that of the cartridge slot.
So you can use a slot expander with a RAM expansion or a MFR+SD, etc, and this extra RAM will be taken as the main memory at startup.

By lkpalwa

Expert (92)

lkpalwa's picture

09-04-2019, 10:21

Nopp I want it internal, without screwing the Cartridge Tongue So I will do some more testing and have reach out in different community groups on FACEBOOK for images from SVI with internal mapper Smile hopefully someone can take images of IC34, IC63, IC35, IC41 and IC63 + plus IC52 .. so waiting for help

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