Interfacing To The Keusb24 I/O Header - Hagstrom KEUSB24 User Manual

Interfacing to the KEUSB24 I/O Header

The 2 x 25 pin dual row header on the KEUSB24 consists of 24
I/O pins with a Logic Ground at one end. The I/O signals are
labeled on the KEUSB24 as "A" through "X". Each pin on the
dual row header is connected in parallel with its adjacent pin.
Therefore, each I/O signal is available on two different pins.
Use the supplied KEUSB24.EXE program to confi gure the I/O pins
as either Rows or Columns. Keystrokes are initiated by shorting
a Row pin to a Column pin through a contact closure. The pins
that are defi ned as Columns will sink current while scanning the
matrix. The Rows are used to read the status of the inputs when
a Column is active.
Column
Column
Row
Figure 1.1
Inputs are activated by
shorting a pin defi ned
as a Row to a pin
defi ned as a Column.
*Note:
The switch, keypad, or input device that is used must
be capable of carrying at least 1mA of current. In addition to
switches and keypads, other electronic circuits may also be used
to generate keystrokes, provided that they do not exceed the 5
volt logic level range of the KEUSB24 I/O.
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