Re: [stella] SRAM cart for 2600?

Subject: Re: [stella] SRAM cart for 2600?
From: Sark <ian.primus@xxxxxxx>
Date: Mon, 21 May 2001 17:50:31 -0500
Thanks for all your help! Have you built this project? How well did it work? 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?
Thanks!

Ian Primus
ian.primus@xxxxxxx

Maximiliam Luppe wrote:

> I lost the instructions about programming. The first three chips in the
> BASE.PCX file are 74374:
>
> 74374
> 8-bit 3-state D flip-flop.
>
>     +---+--+---+             +---+---+---+---+
> /OE |1  +--+ 20| VCC         |/OE|CLK| D | Q |  0  : logic low level
>  Q1 |2       19| Q8          +---+---+---+---+  1  : logic high level
>  D1 |3       18| D8          | 1 | X | X | Z |  X  : don't care, either 0 or
> 1
>  D2 |4       17| D7          | 0 | / | 0 | 0 |  Z  : high impedance
>  Q2 |5   74  16| Q7          | 0 | / | 1 | 1 |  /  : rising clock input
>  Q3 |6  374  15| Q6          | 0 |!/ | X | - |  !/ : not a rising edge
>  D3 |7       14| D6          +---+---+---+---+  -  : no change
>  D4 |8       13| D5
>  Q4 |9       12| Q5
> GND |10      11| CLK
>     +----------+
>
> The last one is 74157:
>
> 74157
> 4-of-8 noninverting decoder/demultiplexer.
>
>     +---+--+---+
>   S |1  +--+ 16| VCC
> 1A0 |2       15| /EN
> 1A1 |3       14| 4A0    S = 0: xY <- xA0
>  1Y |4   74  13| 4A1    S = 1: xY <- xA1
> 2A0 |5  157  12| 4Y
> 2A1 |6       11| 3A0
>  2Y |7       10| 3A1
> GND |8        9| 3Y
>     +----------+
>
> The first '374 stores the lower address (A0-A5 -> DP0-DP5), the A12 address
> line (DP6) and a SEL line (DP7). This SEL line will select the two nibbles
> of the data to be read from the cart (0 -> D0-D3 / 1 -> D4-D7) througt the
> Status Register from Parallel Port.
>
> The second '374 stores the upper address (A6-A11 -> DP0-DP5), the WRITE
> control (DP6) of the Cart and the OE control (DP7) of the third '374.
>
> The third '374 stores the data to be written to the Cart.
>
> The '374s are controled by the AUTO, STROBE and INIT lines of the Parallel
> Port. The sequences to write anr read the cart are:
>
> -WRITE:
>     Send data to Parallel Port Data Register (378h or 3BCh)
>     Clock (0 -> 1 -> 0) the INIT line
>     Send lower address to Parallel Port Data Register, A12(0)* and SEL(X)
>     Clock (0 -> 1 -> 0) the AUTO line
>     Send upper address to Parallel Port Data Register, WRITE(1) and OE(0)
>     Clock (0 -> 1 -> 0) the STROBE line
>     Send upper address to Parallel Port Data Register, WRITE(0) and OE(1)
>     Clock (0 -> 1 -> 0) the STROBE line
>
> -READ:
>     Send lower address to Parallel Port Data Register, A12(0)* and SEL(0)
>     Clock (0 -> 1 -> 0) the AUTO line
>     Send upper address to Parallel Port Data Register, WRITE(0) and OE(1)
>     Clock (0 -> 1 -> 0) the STROBE line
>     Read Parallel Port Status Register (379H or 3BDh) (lower data)
>     Send lower address to Parallel Port Data Register, A12(0)* and SEL(1)
>     Clock (0 -> 1 -> 0) the AUTO line
>     Read Parallel Port Status Register (379H or 3BDh) (upper data)
>
> *The A12 line enables download two games to the cart. The game will be
> selected by the G.Sel switch in the 4KCART.PCX file.
>
> Any 8kx8 SRAM can be used, like 5564 and 6264.
>
> > Good schematics, but what are the chips in the base unit? What software do
> I
> > need to drive it? Are there any substitutions for the RAM chip in the
> cart? I
>
> Any 8kx8 SRAM can be used, like 5564 and 6264.
>
> > can't find that one anywhere. What about recycled PC cache RAM from 486's?
>
> If they are SRAM, no problems.
>
> > Thanks!
> >
> > Ian Primus
> > ian.primus@xxxxxxx
> >
> > Maximiliam Luppe wrote:
> >
> > > Hi, Sark.
> > >
> > > Take a look at
> ftp://kew.sel.eesc.sc.usp.br/Electric/Atari2600/2600dev.zip
> > >
> > > I had another circuit that enables you to conect the 2600 directly to
> the
> > > parallel port, but I missed the schematic file. When I find the printed
> > > file, I'll scan it and place it in the same site.
> > >
> > > Max
> > >
> > > -----Mensagem Original-----
> > > De: "Sark" <ian.primus@xxxxxxx>
> > > Para: <stella@xxxxxxxxxxx>
> > > Enviada em: Sábado, 19 de Maio de 2001 00:13
> > > Assunto: [stella] SRAM cart for 2600?
> > >
> > > > I know that somewhere out there in the "Information Wormhole" there
> are
> > > > schematics for building Atari 2600 SRAM carts and a reader/writer that
> > > > connects to the PC's paralell port. Does anyone have these? Is there a
> > > > web site somewhere with instructions on costructing such devices? If
> > > > anyone can help, I would much appreciate it.
> > > >
> > > > Ian Primus
> > > > ian.primus@xxxxxxx
> > > >
> > > >
> > > > -
>
> -
> Archives (includes files) at http://www.biglist.com/lists/stella/archives/
> Unsub & more at http://www.biglist.com/lists/stella/


-
Archives (includes files) at http://www.biglist.com/lists/stella/archives/
Unsub & more at http://www.biglist.com/lists/stella/

Current Thread