Important notes

• On circuit diagrams, plugs are displayed as viewed from the back side, the solder side. Chips are displayed as viewed from above; also, see the small semicircular cut for finding the correct orientation. When in doubt, see the corresponding description on the legend page.

Construction

You need the following parts to build this cable:

• One power cable

• One solderable 6-pin male DIN plug (Commodore serial plug)

• One solderable 25-pin male plug (PC parallel plug)

• One 7406 inverter IC

• One 74LS86 exclusive-OR IC

• A shielded 3-wire or unshielded 4-wire cable of, preferably, at most 2 meters

Step 1. To make soldering on the IC's easier, you may want to slightly melt the plastic on the inner side of the case of parallel port plug and carefully embed the inverter IC into it. Then shorten pins 1-6, 8-10 and 12-13 of the exclusive-OR IC, glue it on top of the inverter IC and solder the three still long pins of the exclusive-OR IC to those of the inverter IC. You should have the following connections:

Exclusive-OR IC
  Inverter IC  

  7, GND       
   7, GND      

 11, Output 4  
  11, Input 5  

 14, +5V       
  14, +5V      

Note that the pins in each pair are exactly on top of each other.

Step 2. Solder one end of the long cable onto the DIN plug.

Step 3. Solder the other end of the long cable onto the parallel plug and the exclusive-OR IC. You should have the following connections:

   DIN plug   
 Parallel plug 

    2, GND     
 18-25, GND      

    4, CLK     
    12, PaperEnd 

    5, DATA    
    15, Error    

   DIN plug   
Exclusive-OR IC

    3, ATN     
  4, Input 2A 

    3, ATN     
 12, Input 4A 

Step 4. Build the inverter bridges, using the inverter IC. You should have the following connections:

   DIN plug   
  Inverter IC  
  Inverter IC  
 Parallel plug 

    4, CLK     
  6, Output 3  
  5, Input 3   
    16, Init     

    5, DATA    
 12, Output 6  
 13, Input 6   
     1, Strobe   

    5, DATA    
 10, Output 5  

This is equivalent with three inverters whose outputs are pointing towards the pins in the left column of the table and their inputs to the ones on the right. Note that you have already finished the input half of the third inverter bridge in step 1.

Step 5. Build the exclusive-OR gates, using the exclusive-OR IC. You should have the following connections:

 Parallel plug 
Exclusive-OR IC
Exclusive-OR IC
 Parallel plug 

    14, AutoFeed 
  5, Input 2B 
  6, Output 2 
    10, Ack      

    17, SelectIn 
 13, Input 4B 

This is equivalent with two exclusive-OR gates whose outputs are pointing towards the pins in the right column of the table and their "B" inputs to the ones on the left. Note that you have already finished the output half of the second gate in step 1, and the "A" inputs for both gates in step 3.

Step 6. Supply power for the inverter IC and the exclusive-OR IC's, with the power cable. You should have the following connections:

  Inverter IC  
  Power cable  

    7, GND     
      GND      

   14, +5V     
      +5V      

Note that this also gives power to the exclusive-OR IC as you have connected the two IC's together in step 1.

Circuit diagram

The numbers besides the inverters and the exclusive-OR gates show the suggested pin numbers of the inverter IC and the exclusive-OR IC. You don't have to follow these pin numbers exactly, though, as the inverter IC has six and the exclusive-OR IC has four independent circuits which are all equivalent. However, using these pins, you can elegantly pack all the necessary electronics into the plastic case of the parallel plug as one IC can be put on top of the other.

You can find the description of all parts used on the diagrams at the legend page.

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