DIO-500  2xCOM/1xLPT/1xGAME

Manufacturer: DFI inc, 1991.  (http://www.dfiusa.com)

To install the second COM port you need 3 IC's; U1=75189, U2=75188,
 U11=16450. (I suppose that regular 1489 and 1488 can be used
 instead of 75189 and 75188)

  .--------------------------------.
  |               .. ..  :J1: :J2::|.--
  |  ####  ####   :: ::            ||
  |  U1    U2    JP1 JP2 :JP3:    .==.  J3 COM-port
  |                      :JP4:    | ||  9-pol dsub male
  |                  ::           `=='
  |                  JP5            |
  |   .--------.                  .==.                 
  |   |16450opt|U11               | || J4 LPT-port
  |   `--------'                  | || 25-pol dsub female
  |  !!!!       !!!!              | ||
  |  DSW1       DSW2              `=='
  `------nnnnnnnnnnnnnnnnnnnnnnnn--'|
         """"""""""""""""""""""""   |

DSW1 and DSW2 are 8-pin DIP-switches.

DSW1:1  LPT port. OFF=LPT2(378-37Ah)(default), ON=LPT3(278-27Ah).
        If LPT1 is not installed elsewhere in the computer, then
        the ports are redirected: LPT2->LPT1 and LPT3->LPT2.


DSW1:2-3  Serial port.
  COM1=3F8-3FF, COM2=2F8-2FF, COM3=3E8-3EF, COM4=2E8-2EF

     S2   S3   Primary port  Secondary port
     ON   ON   COM1          COM2    (default)
     OFF  ON   COM2          COM3
     ON   OFF  COM3          COM4
     OFF  OFF  ** not allowed **

DSW1:4  Game Adapter. (200-207h)  ON=Enable(default), OFF=Disable.
DSW1:5  Printer port. ON=Enable(default), OFF=Disable.
DSW1:6  (not used)
DSW1:7  Primary   serial port. ON=Enable(default), OFF=Disable.
DSW1:8  Secondary serial port. ON=Enable(default), OFF=Disable.

DSW2:1-8  Secondary serial port.        Primary serial port
               S1  S2  S3  S4                 S5  S6  S7  S8
          IRQ2 ON  OFF OFF OFF          IRQ2  ON  OFF OFF OFF
          IRQ3 OFF ON  OFF OFF (def)    IRQ3  OFF ON  OFF OFF
          IRQ4 OFF OFF ON  OFF          IRQ4  OFF OFF ON  OFF (def)
          IRQ5 OFF OFF OFF ON           IRQ5  OFF OFF OFF ON

JP1  Primary serial port force true DCD/DSR/CTS.
     The two left pins jumpered = default,
     the two right pins jumpered = force true.
     Row 1 = DCD, Row 2 = DSR, Row 3 = CTS

JP2  Secondary serial port force true. Same as JP1.

JP3  Secondary serial port DTE/DCE.
               .-.-.-.-.-.          .---.---.-.
          DTE: | | | | | |     DCE: |---|---| |
     (default) `-'-'-'-'-'          `---'---'-'

JP4  Primary serial port DTE/DCE. Same as JP3

JP5  Printer port IRQ. The two left pins=IRQ7(default),
     The two right pins=IRQ5.

J1  Secondary serial port.  Pin 1 on J2 to pin 1 on 9pinDsub, 2-2...9-9
    or if it's a 25pinDsub: 1-8, 2-3, 3-2, 4-20, 5-7, 6-6, 7-4, 8-5, 9-22.
    Numbering for J1: 2 4 6 8 10
                      1 3 5 7 9

J2  Game Adapter. Pin 1 on J2 to pin 1 on 15polDsub, 2-2....15-15.
    Numbering for J2: 2 4 ... 16
                      1 3 ... 15


--- Tomas Andersson 1996-05-03