Hi Michau, cool progress. A couple of questions/observations. I assume you mean /EXRAM and not /EXROM? Did you determine whether your MAX machine matches the schematic from Ruud or the reversed engineered one from Donato Travaglini? The ones that Steve and I have match the latter and for those, pins 9 & 10 must be jumpered for the CIA to get it's select signal. How will you initialise the latch when you power on? In my prototype I used a 74LS174 which is a hex latch with a master clear tied to the reset line. This way bank 0 of the EPROM is always going to be selected at reset and it meant I have a reset button which always takes me back to the image selection menu. I guess I should get on with finishing the boot menu and ROM image! cheers, Rob On 22/10/2013 10:47, Michał Pleban wrote: > 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 list Message was sent through the cbm-hackers mailing listReceived on 2013-10-22 15:00:05
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