Hello Jim, > I was thinking I could feed the CS1,2,3 lines into the '138 with > jumpers and pullups on the '138 input lines. Then, 8 jumpers to > select which combination was needed for the JEDEC /OE line. That > would handle inversions of any line, but each of the CS lines needs 3 > states: > > connected to nothing > connected to '138 > connected to JEDEC pinout. > > So, I'd need 3 2 way jumpers and 8 1 way jumpers to handle every > combination. 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 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). The last idea can be expanded to a 2308 or 2304 (does the last one exists?) or to use other signal to generate the chip select from the eprom, too. If i remember, the 2308 has only two cs at pins 18 and 20. Pins 19 and 21 are not connected! The MC68x308 (http://bitsavers.org/pdf/motorola/_dataBooks/Motorola_Memory_Data_Book_1979 .pdf page 2-137) has all four pins with the option for chip select. Martin Message was sent through the cbm-hackers mailing listReceived on 2011-08-12 16:00:03
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