Re: [stella] SRAM cart for 2600?

Subject: Re: [stella] SRAM cart for 2600?
From: Sark <ian.primus@xxxxxxx>
Date: Tue, 22 May 2001 17:52:27 -0500
I went and bought parts, but I didn't know what voltage the battery should be.
Would a 3.5v lithium computer battery do?

Ian Primus
ian.primus@xxxxxxx

Maximiliam Luppe wrote:

> > Thanks for all your help! Have you built this project? How well did it
> work?
>
> You are welcome. I didn't build this project, but I can tell you how it
> works. When you place the SRAM Cart in the Base (BASE.PCX circuit), it's
> powered by the +5V line. So you can transfer the data (.BIN ROM file) to the
> SRAM Cart. When you remove the SRAM Cart from the Base, the SRAM still
> retain the data because it will stay in stand-by mode, thanks to the Batt.
>
> The Cart Connector Pin 12 is tied to ground in the VCS, but it's used to
> write enable the SRAM in the Base.
>
> > I took a Pac Man apart, and desoldered the ROM chip. I dug through my bin
> of
> > scavenged chips, and found some SRAM's They are UM61256AK-15's. I checked
> on
> > the 'net, and they are 32k*8 SRAM chips. Will the larger chips work as
> 8k*8
> > chips?
>
> Yes, but you'll have to make some modifications in the circuit. See the
> following circuit:
>
>  Cart       +---+--+---+
>  Con.----1A |1  +--+ 14| VCC
>  Pin 6  /1Y |2       13| 6A
>  (A12)   2A |3       12| /6Y
>         /2Y |4  7414 11| 5A
>          3A |5       10| /5Y
>         /3Y |6        9| 4A
>         GND |7        8| /4Y
>             +----------+
>
>                     +-----+--+-----+
>            .----A14 |1    +--+   28| VCC
>            |    A12 |2           27| /WE
>            |     A7 |3           26| A13----.
>            |     A6 |4           25| A8     |
>            |     A5 |5           24| A9    ---
>            |     A4 |6           23| A11    -
>            |     A3 |7   61256   22| /OE
>            |     A2 |8           21| A10
>            |     A1 |9           20| /CE
>            |     A0 |10          19| D7
>            |     D0 |11          18| D6
>            |     D1 |12          17| D5
>            |     D2 |13          16| D4
>            '--,-GND |14          15| D3
>               |     +--------------+
>              ---
>               -
> The modifications are:
>     SRAM pin 1 (old N.C.) must be tied to ground
>     SRAM pin 26 (old CS2) must be tied to ground and the connection to Cart
>         Connector Pin 6 (A12) must be removed
>     74HC14 pin 1 must be connected to Cart Connector Pin 6. The resistor and
>         the +5V connection must be removed.
>     The rest remains equal.
>
> > Thanks!
> >
> > Ian Primus
> > ian.primus@xxxxxxx
> >
> > Maximiliam Luppe wrote:
> >
> > > I lost the instructions about programming. The first three chips in the
>
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