Hello Jim, > The issue with that is the D0-D7 can't be left unconnected, so they > need to be pulled to Vcc with jumpers to ground. That's right. > That's 8 resistors > + 3 for the CS line pins + 3 for the additional address lines (3 + 3 > + 8 = 14). No, you need only the 8 reststors and jumpers for D0-D7. The CS where direct connected to A, B and C. No restistor is needed! If you have a "dont't care" CS, you put an additional jumper at D0-D7. E.g: CS1 it low aktiv, CS2 is don't care and C3 is high aktiv CS3/CS2/CS1 1 0/1 0 => Jumper 4 and 6 > The '138 approach requires only the resistors for the 3 > incoming CS lines and the 3 additional address lines (A13,14,15 - the > design allows use of EPROMS/FLASH up to 27C512) I can still do > through hole with 6 resistors, but not with 14. Okay, with the 151 you need 11 restistors. So you can jumper any combination of the CS! >> The other way is to use a comparator eg. 688. > I think you meant '85. No, the 85 hasn't an inverted output signal. You need an additional inverter... > '688 is an 8 bit comparator, no need for that much... That's true, but i think not the problem. It's a standard typ. Unused pins can be grounded. Martin Message was sent through the cbm-hackers mailing listReceived on 2011-08-14 11:00:09
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