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/
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