SX-1 Switch to disable FMV possible ?

[Rochabian]

SX-1 allows one 8MB memory SIMM to be installed and when a FMV card is detected, only 4MB memory are available because the other 4MB memory are taken by the FMV module.
You don't have to change jumpers or anything, autoconfig automatically limit the memory to 4MB when FMV is present

What i want to do is to put a FMV disable switch, probably from the riser of the SX-1 (i don't want to solder anything on the FMV Card), to be able to choose for 4MB memory + FMV or 8MB for WHDLoad use, and because i don't want to remove the FMV module many times, because connections are fragile

I 've seen that on the CD32 connector, only 3 pins carry the 12V
If i cut the 3 traces from that pins and add a switch between them, will it be sufficient to disable the FMV ?

+5V is carried by 12 pins, so it's harder to cut them all........


Do someone tried this or think of another way to do this as i don't know if cutting 12V will be sufficient to disable FMV card....

[Rochabian]

I think before cutting the traces i will desolder the three 12V pins and see if the card is still detected, could be safer.......

[derSammler]

I doubt the FMV module even uses 12V. The logic works with 5V.

Also, it's probably not wise to do it that way. Check the schematic for the FMV module to see if there is a proper way to disable it. (that is, if the schematic is available)

[Rochabian]

Yes it's a "brutal" method, will be better if there was a disable jumper but there is none.

Schematics are available, and as you said, most of the logic use 5V

12V seems only used for a LC78835M (U310 ), it seems to be a DAC and a 78L05 (U311) that is a voltage regulator. I'm not sure it will be sufficient to hide the card.

Best way can be a switch to disable the ROM but needs soldering on the FMV card...or perhaps with the addition of another ROM support on top of the existing one and modify it to put a switch .

The risk is that the card could be seen "faulty" by the CD32 instead of hiding it

I'm not sure from which way i'll try


EDIT:

I've tried to boot after removing the FMV ROM, but then the FMV Board AND the SX-1 are hidden, so it's not the right method

[Rochabian]

Well, i think it's not possible without adding logic to the riser.
Just disabling the power line of some chips will not work....

Adding logic and a switch to completely disconnect the FMV slot from the riser seems to be the only way, way beyond my skills

[Rochabian]

Is there a way to play with the AUTOCONFIG thing to disable an add-on board ?

I've seen that autoconfig send a signal to the board and if there is no response, the board is ignored or a "shut up" command is send to the board.

Someone knows how autoconfig signals are sent on the cd32 expansion connector ?

It could be interesting to have a switch to allow or not the signal to be sent to the board and then disable or not the board.

But perhaps it's not as simple as that.......

[alexh]

CIOUT pin 100
CIIN pin 107

These are the two autoconfig daisy chain pins on the CD32 expansion connector.

There must be equivalents on the SX-1 where the FMV unit plugs in that you could potentially disconnect / bypass using a switch.

I don't think it is as simple as this but you never know.

[Rochabian]

Isn't pin 107 CIIN & 108 CIOUT ? Probably you've made a mistype with pin 100

I've found pin 133 CONFIG OUT & 134 CONFIG IN too

Are you sure it's 107 & 108 for autoconfig or it could be 133 & 134 ?

I could eventually mask those pins on the FMV module to see how it behave

[alexh]

Originally Posted by Rochabian

Isn't pin 107 CIIN & 108 CIOUT ? Probably you've made a mistype with pin 100

Yes it was 108 but I couldn't read the schematic because it's a very poor scan.

https://cd32.amiga32.com/tech/cd32-expansion.png

Originally Posted by Rochabian

Are you sure it's 107 & 108 for autoconfig or it could be 133 & 134 ?

You are right, the correct pins are 133 and 134.

https://www.manualslib.com/manual/21...page=28#manual

Maybe 107 & 108 are only used if you have a CPU accelerator (which the SX-1 doesn't have).

[Rochabian]

Thanks for confirming the right pins

I've masked pin 133 & 134 and the board is not detected anymore in the expansion board diagnostic. Test was done with the FMV original riser only (less risk of breaking something)

Now i have to try same thing with SX-1 + FMV, i think at worst it will just not boot

[Rochabian]

On SX-1 with FMV card pin 133 & 134 masked , it boots but both SX-1 & FMV card are hidden......

It's the pin 133 CONFIG OUT, when masked, that disable the board

The FMV card should communicate with SX-1 on other pins too....But wich ones ???

Apparently autoconfig is a chain and board 1 configure board 2 etc...

The FMV card is seen as board 1 in the expansion board diagnostic and SX-1 as board 2, i think that's why SX-1 and FMV are disabled when i "cut " pin 133 on th FMV card

But how it works when there is no FMV card then ? The FMV card surely return unwanted signal to the SX-1 although pin 133 is disabled

Perhaps some logics are still active and needs to be disabled too, i have to tests masking other pins too

In fact pin 133 an 134 goes directly to the FMV rom, that's why i have the same result as removing the FMV rom from the board, the 2 boards are hidden then

[alexh]

But if you don't plug the FMV in... what drives CONFIG_OUT?

[Rochabian]

It can be a logic that detects the presence of the FMV board on the SX-1, independently from AUTOCONFIG, and then route the CONFIG IN or not to the FMV card

For example if the FMV card is present (detected by another signal ), then CONFIG IN is routed to the FMV card from the SX-1, if not, the SX-1 answer with his CONFIG OUT signal

As we don't have SX-1 schematics......hard to tell

Like you said, it won't be that simple

[Jope]

In an A2000 it's some pulldown resistors and a 74ls32 or gate that handles the empty slots in the autoconfig chain.

[Rochabian]

Originally Posted by Jope

In an A2000 it's some pulldown resistors and a 74ls32 or gate that handles the empty slots in the autoconfig chain.

Interesting !

I'll check if a similar system could have been used on the SX-1 or the riser.

I'll follow the pins 133 & 134 to see where they go on the SX-1

[alexh]

Originally Posted by Rochabian

I'll follow the pins 133 & 134 to see where they go on the SX-1

Follow them back from where the FMV plugs in. Those are the pins which need masking.

[Rochabian]

Pins 133 & 134 go to this chip, which is a
programmable logic IC, so it's hard to tell what it does
I have to check where all his pins goes on the board, to try to understand how it could work
There is no logic at all on the SX-1 riser, only some resistors for the audio DIN connector

EDIT: It's an AND/OR PIC so i assume it's the chip that control where CONFIG IN & CONFIG OUT are routed if it detects or not the addition of the FMV module

[Rochabian]

I tried to find where all the pins go

I thing this chip is related to autoconfig but i really don't know how it works

I tried to lift pin 23 (CONFIG IN) and it changes absolutely nothing, it works normally, FMV detected when present and only 4MB of RAM or 8Mb when FMV not present...

CONFIG OUT SEEMS only connected to a pulldown resistor on the SX-1, it doesn't go this this chip i think

Notice that the extra 4MB take place of the FMV when the FMV module is not present because it uses the same adress

So when no FMV and 8MB SIMM in SX-1

Board 1 -> 2nd bank of 4MB RAM
Board 2 -> SX-1 and 4MB RAM

With FMV and 8MB SIMM in Sx-1

Board 1 -> FMV Module
Board2 -> SX-1 and 4MB RAM

And with only 4MB of RAM and no FMV

Only Board1 -> SX-1 and 4MB RAM

As FMV or 2nd 4MB RAM share the same adress, i think the SX-1 could check if a FMV is present, perhaps trying to reach the BOARD ID NIBBLE adress, if ok then configure the FMV MODULE + SX1 or if not present 2nd 4Mb RAM + SX1

The FMV module is detected by the SX-1 although the PIN 134 is masked on the FMV module, so there is another check done by the SX-1, surely on the BOARD ID NIBBLE.

As the gayle implementation seems particular on the SX-1, perhaps it's the same with the AUTOCONFIG thing.....