TDT RZ2 Manual page 638

17-20
Resetting the Latch...
In the previous examples all button presses are acquired, that is, if a person presses
buttons simultaneously there is the chance that both responses will be obtained. This
will happen infrequently with circuits that use an iCompare and Latch, but it is still
possible. In some cases the user will want to determine if the proper button press
was acquired or wait until a particular button press has happened. Additional circuitry
can be added that checks for this.
Identifying the correct button press...
In this example, the top part of the circuit detects if a button is pressed. The button
press value is also translated into a value representing which bit was read. For
example, if the bit in bitmask value is 16, then Log2 converts the value to 4. This
lets the user determine, via the Button_Press parameter tag, that bit 4 was high.
The lower part of the circuit tests to determine if the correct button was pressed. If
so, an LED is flashed. A parameter tag is used to identify the correct button press.
The iCompare is only triggered when the correct button is pressed. The EdgeDetect
component then sets the Schmitt that turns on the first LED for 100 milliseconds.
Button box circuits can be incorporated in to all TDT System 3 software. For
information on using the button box with other applications please see that
application's documentation. If you have questions about how to design your own
applications for the button box call 386-462-9622 for technical assistance.
BBOX Button Box
System 3