Specifications

APPENDIX C: EVENT PROGRAMMING
Page 183 MRC-565 Packet Data Radio Operations & Maintenance
trigger the next time the voltage goes to or above 5.0 volts. The event action is not triggered
when the voltage crosses the 5.0 level in the downward direction, only the upward direction. If
one wants to detect both voltage crossings, there should be two events defined, one to detect the
positive change (ADCHI), and one to detect the negative change (ADCLOW).
The settling and hold-off durations are programmable for each scanned event. They are specified
in clock-tick counts where each tick is 62.5 milliseconds, or 1/16 second. Because these
durations are programmable, scanned event hysteresis is fully controllable. Given the 62.5
millisecond sampling rate, events are limited to those that persist longer than 62.5 milliseconds
but shorter than about an hour duration. Similarly, hold-off times between events must also
persist longer than 62.5 milliseconds. Attempting to program events that are briefer than 62.5
milliseconds will prove unreliable. It is important to remember that a scanned event must
change slow enough that the event monitor can sample the input line reliably.
The external I/O expander (XIO) has its own processor to scan its event definition table. Its
internal "clock-tick" will be set to one millisecond per increment. The MRC-565 will configure
the XIO when event commands are processed from the script file. The XIO will monitor its own
events and send changes to the MRC-565 using a serial interface.
Discrete Event
A discrete event is determined by whether or not a discrete input signal remains either high or
low for the given settling duration. "high" or "low" is a part of the event definition set by the
operator. The end of a discrete event occurs when the signal has persistently returned to its
previous low or high state for the hold-off duration. For RS 232 signals, "high" is considered the
ON state and "low" the OFF state. "high" is also known as SET; "low" as CLR.
The high/low convention follows the voltage level of the input signal. For TTL signals, "high" is
a +5 volt level, and "low" is zero volts. For the RS-232 modem-control signals, "high" is +10
volts and "low" in -10 volts. For the GPS input, a "high" is when the GPS is at "V1" or "V2"
status, and "low" is when there is no GPS characters being received at the RS-232 port or when
the GPS is at the "V0" status. The NET input is "high" when the RF modem is online to a Base
or Repeater that is connected to a host system. The NET "low" input indicates the RF modem is
offline to a Base or Repeater.
Analog Event
An analog event is determined by whether or not an analog input signal remains above or below
a threshold for the given settling duration. "Above" or "below" and the threshold level are also
given in the event definition. The end of an analog event occurs when the signal has persistently
returned to the non-event side of the threshold for the hold-off duration.