02/13/11: CoCo Cassette Port Pins by Roger, | Category: Peripherals, Programming | Comments are closed

CoCo Cassette Port Pins

Cassette port pinout


The cassette cable has a 5-pin DIN connector on one end, that plugs into the back of the CoCo; the other end has three earphone-style plugs, that plug into the EAR, AUX (or MIC), and REMOTE jacks. The remote-control plug is smaller than the other two. The other two are differentiated by color: the black one plugs into the EAR jack, while the grey one plugs into AUX.

Here is an ASCII drawing of that connector, including a pinout and showing how the pins are numbered. The drawing is of the connector at the end of the cable, with the pins pointing toward you. So if you are looking at the back of the machine, at the connector there, this pinout is backwards. My apologies for the wacky numbering; this is the same numbering as in the CoCo-1 technical manual.


        -------       Pin#  Name      Connects to
      /  \___/  \     ----  -------   -----------------------------------
     /           \     
    /             \    1    CASSMOT   SG stem
                       
   |               |   2    GND       B stem, LG stem
   |  1o       o3  |   
   |               |   3    CASSMOT   SG tip
        o     o        
    \  4   o   5  /    4    CASSIN    B tip
     \     2     /     
      \         /      5    CASSOUT   LG tip
        -------       

                         B=black    SG=small grey    LG=large grey

The names are given from the perspective of the computer, so “OUT” means output from the computer, input to the cassette, and it should go into the AUX (or MIC) jack while the cassette is recording.

The “connects-to” column show which of the three earphone-style plugs the wire leads to, and to which part (stem or tip).

Below is another cheesy ASCII drawing, this time of one of those plugs. The cylindrical prong actually consists of two metal parts, separated by a narrow strip of plastic, drawn as “X”s. The stem section is much longer than the tip section, and the tip section has a groove around it, so that a spring loaded contact can hold it in place a little bit when it is inserted into a jack.


              -------------
              |           |
              |           |------------xx-\  /--\
              |           |            XX  --    |
              |           |  "stem"    XX   "tip"|
              |           |            XX  --    |
              |           |------------xx-/  \--/
              |           |
              -------------

For both of the plugs that carry data (the large ones), the stem is connected to ground, and the tip is the data line.

For the motor-control plug (the small plug), it shouldn’t really matter which of its two wires connects to its tip and which connects to its stem; you could just as easily connect 1 to SG tip and 3 to SG stem, and it should still work fine. These two wires are just connected together by a relay in the computer when it is time to let the motor run. The wiring shown here matches my cassette cable

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