6. CONNECTION OF I/O UNITS TO
- Preventing malfunctions that may be caused by detouring current
When there are three or more matrix DI points, detouring current
can cause a nonexistent DI input to be falsely detected as existing.
As shown below, if KY01, KY03, and KY21 are closed
simultaneously, current detours through the path indicated with
arrows, thus causing a false input of *KY23 to be detected because
of a current path formed by a combination of common signal
*KYC2 and data signal *KYD3.
Two modes are available to prevent this malfunction. One should
be selected according to the user applications.
D Ignoring all occurrences of three or more simultaneous inputs
Action : Make the *MNDI signal open (see item “D Key
If there are two inputs and a third is added, all three
are ignored. When one of the three inputs is
removed, two are accepted.
D Attaching detour prevention diodes to enable three
Action : Connect the *MNDI signal (see item “D Key switch
addresses”) to 0V.
A diode must be connected in series with a switch,
as shown below.
Detour prevention diode
D Mode selection