On 8/12/2011 10:54 AM, Hoffmann-Vetter, Martin wrote: > Hello Jim, > > > Or you use a 151. But 8 jumpers at the inputs D0 to D7, wire the 3 chip > select signal to A, B and C und the output signal W to the chip select of > the eprom. The strobe input must be grounded. > Now you can put 1 or more jumpers and programm the used chip select signals. > So you can use it for the 2332 (two jumpers) and 2364 (four jumpers). 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 8 resistors + 3 for the CS line pins + 3 for the additional address lines (3 + 3 + 8 = 14). 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. > > The other way is to use a comparator eg. 688. You wire the chip select > signal to A0, A1 and A2, put B0, B1 and B2 with pullups and put an 3 pin > jumper to connect to ground or Ax. The output is the chip select signal for > the eprom. So any jumper position has 3 state: > * don't care (connected Ax and Bx for a logic 1, always true) > * must be 1 (is only true if Ax is logic 1) and > * must be 0 (is only true if Ax is logic 0). This might work. I discarded it early, but it would only require 3 2 way jumpers, and 6 resistors, so I should consider it. > -- Jim Brain email@example.com www.jbrain.com Message was sent through the cbm-hackers mailing listReceived on 2011-08-13 04:00:12
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