IMPORTANT: You can now order custom cartridges from Atari Age. Of course, this page is still useful for anyone who is learning electronics or just likes to tinker.
The F8 bankswitch convention works the following way: Address 1 1111 1111 1000 Go to bank 0 1 1111 1111 1001 Go to bank 1 ---------------- PinName A AAAA AAAA AAAA 1 1198 7654 3210 2 10 One way to do this is to put a detection circuit on A1-A12 which clocks A0 into a flip-flop as the bank value. There may be easier/cleaner ways to do this but I think three chips (7404,7474,74133) with a deglitching cap isn't that bad. |\ -------------| >()-------------- Eprom | |/ Enable | 5v 5v A12 -+-|- __|___|_ A11 ---| \ | Set Rst| A10 ---| \ | | A9 ---| 7 \ A0--|D 7 Q|-- A12 A8 ---| 4 N \ | 4 | of eprom A7 ---| 1 A | |\ | 7 | A6 ---| 3 N |()-+-| >()---|> 4 | A5 ---| 3 D | | |/ |________| A4 ---| / | A3 ---| / ___ /A2 ---| / ___ 1000pf (0.001 uf) /A1 ---| / | \--|_/ | gnd Eprom must be tied to 2600 D0-D7 and A0-A11 directly /A1, /A2, A12, Nand output inversions done with 7404 chip /A1 goes to two pins on the NAND gate because it has 13 inputs. You can use some other signal though The 2600 A12(cart enable) and eprom A12 are completely separate animals The 7474 is a dual D flip-flop, you can use something equivalent Stargate (Defender II) is the only F8 game that uses the Atari Ram. It won't work without it. If you're making a multicart, put two 4k games at the front or end of the eprom. Do NOT put one or three or an odd number, you'll screw up the 8k address boundaries. Check that a 4k game works, then try F8 games so you're not trying to troubleshoot everything at once. If it works with 4k games but not F8, and you are sure it's wired correctly, you may need to play with that cap value, it might be sensitive to the IC logic family and speed. You can also try putting three inverters in a row and put a cap in the middle, maybe even with a serial resistor. Here are the part pinouts: +---+--+---+ _____________ A |1 +--+ 16| VCC /Y = ABCDEFGHIJKLM B |2 15| M C |3 14| L D |4 74 13| K E |5 133 12| J 13-input NAND gate. F |6 11| I G |7 10| H GND |8 9| /Y +----------+ 7474 Dual D flip-flop with set and reset. +---+--+---+ +---+---+----+----*---+---+ /1RST |1 +--+ 14| VCC | D |CLK|/SET|/RST| Q |/Q | 1D |2 13| /2RST +===+===+====+====*===+===+ 1CLK |3 12| 2D | X | X | 0 | 0 | 1 | 1 | /1SET |4 7474 11| 2CLK | X | X | 0 | 1 | 1 | 0 | 1Q |5 10| /2SET | X | X | 1 | 0 | 0 | 1 | /1Q |6 9| 2Q | 0 | / | 1 | 1 | 0 | 1 | GND |7 8| /2Q | 1 | / | 1 | 1 | 1 | 1 | +----------+ | X |!/ | 1 | 1 | - | - | +---+---+----+----*---+---+ +---+--+---+ +---*---+ _ 1A |1 +--+ 14| VCC | A |/Y | /Y = A /1Y |2 13| 6A +===*===+ 2A |3 12| /6Y | 0 | 1 | /2Y |4 7404 11| 5A | 1 | 0 | 3A |5 10| /5Y +---*---+ /3Y |6 9| 4A GND |7 8| /4Y Hex inverters. +----------+