Specifications

Table Of Contents
APPENDIX C: EVENT PROGRAMMING
Page 186 MRC-565 Packet Data Radio Operations & Maintenance
Example 2: A Scanned Event - Marker-Drop
Suppose the MRC-565 is wired to detect a marker-drop pushbutton using the CTS and DTR
signals wired to a pushbutton switch mounted somewhere in a vehicle or aircraft. The CTS
output is used to enable switch detection. The DTR input is the input signal on which marker-
drop is detected. Normally open, the switch prevents DTR from receiving the CTS signal. If CTS
is enabled and the marker-drop button pressed such that the switch closes, the CTS signal is
presented to DTR.
To make the marker-drop mechanism function, the CTS signal must be enabled so that it can be
detected at DTR should the switch close. A good time to enable CTS – set CTS to high – may be
when the MRC-565 is powered up. The command EVENT,RESET,SET,CTS will do this. The
event is RESET. The action is SET,CTS. The "ignition" bit should also be set in the status
word, the command EVENT,RESET,SET,BIT2 will set the ignition bit. The bits of the status
register are numbered from low order to high order, BIT0 through BIT15. The MARK bit is the
same as BIT3, and the action "MARK" is used instead of "SET,BIT3" for clarity.
The command EVENT,DIOHI,DTR,16,160,MARK defines an event that creates a vehicle
collision report if the DTR signal is high for 1 second (16 sixteenths of a second). The event will
clear and be ready for another event if the signal is low for 10 seconds (160 sixteenths of a
second). "DIOHI" means "discrete I/O high" and "DTR" specifies the DTR discrete input. The
parameters "DIOHI,DTR,16,160" define the event. The parameter "MARK" defines the
action.
MCC-545 RF Modem
CTS
DTR
Marker-Drop
Switch
CTS is set on reset in order to have a signal to detect on DTR
DTR is scanned every 1/16 second for the high condition