



                        PINOUT OF 2864 AND 2764



          2864                      2764
          28C64                     27C64
       Ŀ Ŀ               Ŀ Ŀ
==> nc  1  28 VCC    ==>Vpp  1  28 VCC
   A12  2     27 !WE<==    A12  2     27 !PGM<==
    A7  3     26 nc         A7  3     26 nc
    A6  4     25 A9         A6  4     25 A9
    A5  5     24 A8         A5  5     24 A8
    A4  6     23 A10        A4  6     23 A10
    A3  7     22 !CE        A3  7     22 !CS
    A2  8     21 A11        A2  8     21 A11
    A1  9     20 !OE        A1  9     20 !OE
    A0 10     19 D7         A0 10     19 D7
    D0 11     18 D6         D0 11     18 D6
    D1 12     17 D5         D1 12     17 D5
    D2 13     16 D4         D2 13     16 D4
   GND 14     15 D3        GND 14     15 D3
                      

nc    = denotes pin not conected internaly
==>   = denotes pins that differ in function from 2764 to 2864



       USING THE 2864 IN PLACE OF THE 2764


       In most cases, you can insert the 2864 directly into the 2764 socket,
since pin 1 is not connected, it is indiferent if it is connected to whatever
other pin or not, and pin 27 (!WE) has roughly the same function that pin 27
of 2764 (!PGM).

       You will need to modify the pinout of the 2864 only if the pin 27 of
the 2764 socket (!PGM) is not tied to VCC. This is very unlikely, since the
2764 doesn't work well if the pin 27 is not tied to VCC. In such unlikely case,
you must lift (bend) the pin 27 of the 2864 (!WE) and solder it directly to the
pin 28 (VCC). Note that the pin 27 will no longer be inserted to the socket.


Ŀ<-- Notch
             2864 (SIDE VIEW)             
ĺĺĺĺĺĺĺĺĺĺĺĺ͹<--- Lift pin 27 and solder pin
                                    27 to pin 28
  15 16 17 18 19 20 21 22 23 24 25 26 27 28


Note 1: When bending the pin 27 be careful not to break the lead. Bend the lead
        only enough so it does not insert in the socket, and use a short piece of
        wire to solder it to pin 28.

Note 2: An 2864 modified as above can be inserted in *any* socket that is
        wired to support an 2764, 27128, 27256 and even 27512. If the socket
        is supposed to receive an 27128, 27256 or 27512, but only 8Kb or less
        of the capacity of the EPROM is needed then this scheme can be very
        useful.







Note 3: When you need to reprogram the 2864, the pin 27 must be dessoldered
        and turned back to its original position, since it is needed in the
        programming proccess.

Note 4: If the socket you will insert the 2864 needs the bending of the pin
        27 and you need to reprogram the 2864 too often, it is likely that
        the pin will break soon. In such case, use the adapter board shown in
        the files ADE2P???.??? instead.




                      PINOUT OF 28256 AND 27128/256/512



          28256                     27256                     27128
          28C256                    27C256                    27C128
       Ŀ Ŀ               Ŀ Ŀ               Ŀ Ŀ
==>A14  1  28 VCC    ==>Vpp  1  28 VCC    ==>Vpp  1  28 VCC
   A12  2     27 !WE<==    A12  2     27 A14<==    A12  2     27 !PGM<==
    A7  3     26 A13        A7  3     26 A13        A7  3     26 A13
    A6  4     25 A9         A6  4     25 A9         A6  4     25 A9
    A5  5     24 A8         A5  5     24 A8         A5  5     24 A8
    A4  6     23 A10        A4  6     23 A10        A4  6     23 A10
    A3  7     22 !CE        A3  7     22 !CS        A3  7     22 !CS
    A2  8     21 A11        A2  8     21 A11        A2  8     21 A11
    A1  9     20 !OE        A1  9     20 !OE        A1  9     20 !OE
    A0 10     19 D7         A0 10     19 D7         A0 10     19 D7
    D0 11     18 D6         D0 11     18 D6         D0 11     18 D6
    D1 12     17 D5         D1 12     17 D5         D1 12     17 D5
    D2 13     16 D4         D2 13     16 D4         D2 13     16 D4
   GND 14     15 D3        GND 14     15 D3        GND 14     15 D3
                                     


          27512
          27C512
       Ŀ Ŀ
==>A15  1  28 VCC
   A12  2     27 A14<==
    A7  3     26 A13
    A6  4     25 A9
    A5  5     24 A8
    A4  6     23 A10
    A3  7     22 !CE
    A2  8     21 A11
    A1  9     20 !OE
    A0 10     19 D7
    D0 11     18 D6
    D1 12     17 D5
    D2 13     16 D4
   GND 14     15 D3
       

nc    = denotes pin not conected internaly
==>   = denotes pins that differ in function from 28XX to 27XX
