commodore 8032 64k extension

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commodore 8032 64k extension

Didier Derny
Do you have any idea of the method used by Commodore  to block the
transfer between the motherboard and the 64k ext

when the cpu is reading / writing in the extension....


I try to follow the tracks but apparently phi2 is not connected directly
to the connector linked to the cpu on the motherboard

so I have the feeling that they are blocking phi2 to avoid any transfer


any idea ?


thanks


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Re: commodore 8032 64k extension

Steve Gray
Looking at the schematics, I think you're probably correct. The 02 signal turns into B02 (page 1) which is combined with /BA15 (page 6) which produces a /RAMON signal which is used to enable the BDx (Buffered Data) lines (back to page 1).

It's a little confusing since they spread the circuitry over two pages that reference each other...

Steve



From: didier derny <[hidden email]>
To: [hidden email]
Sent: Thursday, March 1, 2018 3:42 PM
Subject: commodore 8032 64k extension

Do you have any idea of the method used by Commodore  to block the
transfer between the motherboard and the 64k ext

when the cpu is reading / writing in the extension....


I try to follow the tracks but apparently phi2 is not connected directly
to the connector linked to the cpu on the motherboard

so I have the feeling that they are blocking phi2 to avoid any transfer


any idea ?


thanks


      Message was sent through the cbm-hackers mailing list


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Re: commodore 8032 64k extension

Didier Derny
Hi Steve :)

any place where I could find the schematics for the 64k extension for the 8032 ?
I only have the schematics for the 8296

I also checked the pin of the 6502 connected directly to the connector
most pins are directly connected except  A8..A15  (connected to a 74LS244)  Hi guess they are force Hi-Z when the board is active
R/W and D0..D7 are directly so  a fake read must not come from the main board
I've not been able to track phi2 on the 64k extension the pins on the connector and the 6502 looks like not connected at all
I guess I'll have to remove the connector and the 6502 socket to find the tracks

one of the NC pin the 6502 is connected to the connector I guess it's the signal to disable the rom

till no my hypothese is that when the board is active they are forcing the address on the mainboard to FFXX
and perhaps using the signal to disable the rom to force the mainboard to do a read/write in the void

I guess I have to explore the 8032 schematics to confirm...

the case of the 8296 board is slightly different both are on the same board
and the can inhibit (naturally) the operation on $8000..$FFFF of the board
while working on the 64 extension



Le 02/03/2018 à 01:08, Steve Gray a écrit :
Looking at the schematics, I think you're probably correct. The 02 signal turns into B02 (page 1) which is combined with /BA15 (page 6) which produces a /RAMON signal which is used to enable the BDx (Buffered Data) lines (back to page 1).

It's a little confusing since they spread the circuitry over two pages that reference each other...

Steve



From: didier derny [hidden email]
To: [hidden email]
Sent: Thursday, March 1, 2018 3:42 PM
Subject: commodore 8032 64k extension

Do you have any idea of the method used by Commodore  to block the
transfer between the motherboard and the 64k ext

when the cpu is reading / writing in the extension....


I try to follow the tracks but apparently phi2 is not connected directly
to the connector linked to the cpu on the motherboard

so I have the feeling that they are blocking phi2 to avoid any transfer


any idea ?


thanks


      Message was sent through the cbm-hackers mailing list