Hello! Yesterday I was on a 8 hour train journey, so to kill time I designed the UltiMax cartridge and laid out a PCB for it. It looks like everything just fit on the cartridge PCB I got from Ruud. Here's how it is supposed to work. Sorry I don't have a schematic yet; generally I don't believe in schematics and I always lay PCBs without one. Maybe on a next train journey I'll have time to draw it :-) But here's what I got on the PCB: * A 27C801 EPROM. * A 6116 SRAM. * All needed address and data lines connected properly to these. * A 74LS273 resettable latch, with outputs Q0-Q5 going to high address lines of the EPROM, and Q7 used as below. * A 74LS08 and 74LS04 for glue logic. The idea is that initially, the latch sits at the /EXROM line. This is done as follows: 74LS273.CLK = /EXROM & 74LS273.Q7 So as long as we write values to the latch with it 7 set to 0, the latch still operates. But if we set bit 7 to 1, the latch becomes inactive. In such case, the RAM will become active, because: 6116.CS = /EXROM & ! 74LS273.Q7 So to enable a cartridge, we write correct bank number to the latch ORed with $80. The latch disappears and the RAM takes its place. Of course, there are some other needed signals: 27C801.CS = /ROMH & /ROML 27C801.A13 = /ROML 27C801.OE = 6116.OE = ! RW 6116.WE = RW I need to verify the PCB now and I will send it for prototype production. Regards, Michau. Message was sent through the cbm-hackers mailing listReceived on 2013-10-22 09:00:03
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