***** DDT CONSTRUCTION NOTES *****

July, 1995

The DDT contains four programmable parts namely the EPROM, DDTPAL, DDT1 
and DDT2.  

The PC board is silk screened to identify where the various parts are 
to be located.  A few notes are necessary to clarify some part types 
and jumper locations:

     All resistors are 10k Ohms except for the following as noted on 
the PC board;
          R4  = 100 ohms
          R9  = 1k ohms
          R10 = 100 ohms

     All capacitors are 0.1uF except for the following;
          C1  = 10 uF > 6v tantalum
          C6  = 470 pF ceramic disk
          C16 = 220 pF ceramic disk
          C18 = 220 pF ceramic disk
          C19 = 22uF >6v electrolytic

There is a trace missing on the P.C. board so it is necessary to run a 
wire from the bottom of C19 to the top of C17. This connects the bottom 
of C17 to the +5V supply line.  The schematic may differ about some of 
the above component values.  These values are not super critical but I 
recommend you follow my instructions above.


The DDT16 (][GS) version does not use Q1 or R5.  For the DDT8 (//e) 
version Q1 is a 2N3904 or equivalent and R5 is 10k ohms.


           VP  <-- not used
          ---
         | o |
          ---             DDT16  or  DDT8

          ---              ---        ---
         | o |            | o |      | o |
         |   |            | | |      |   |
         | o |            | o |      | o |
         | | |            |   |      | | |
         | o |            | o |      | o |
          ---              ---        ---
           J1               J2         J2


     Jumper J1 should always be connected between the bottom 2 holes, 
that is the 2 holes closest to the edge connector. The VP hole is not 
used.

     Jumper J2 is connected across the top 2 holes when building a 
DDT16 (][GS operation) and is connected across the bottom 2 holes when 
building a DDT8 (//e operation).

     Please note that a DDT16 will not work in an Apple //e and a DDT8 
will not work in an Apple ][GS.  In addition to the jumper changes 
mentioned above, the DDT8 and DDT16 have different programs in the 
EPROM, DDTPAL, DDT1 and DDT2 chips.

                             S1
                              ----------
                             |o        o|
    Push   -------------------|---- __/ |
    Button                    |    |__  |
    Switch -------------------|----   \ |
                             |o        o|
                              ----------

     S1 is the connection point for an external push button switch.  
The switch is wired to the 2 right holes.  The 2 holes on the left are 
used for a connecting a cable anchor (a piece of wire pulled tight 
against the cable and soldered to the PC board makes a very good 
anchor).  The cable should be 2 conductor unshielded stranded wire.

     The complete schematic is included on this disk along with the 
source code for both the DDT8 and DDT16.

     I would recommend using sockets for all the ICs, it makes trouble 
shooting and repair much easier.

     Two good sources for purchasing any other parts you might need are 
JDR Microdevices (1-800-538-5000) and Jameco (1-800-831-4242).

     I hope you have fun and find this kit useful.

Chuck Kelly
ProDev, Inc.

