Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 57)

Chapter 4
Configuring Your Decoder
4–30
2) Host - If you select host triggering, the decoder will trigger on when a
host start scan command is received and trigger off when one of the
following occurs:
•
Fields per package count is met.
•
Stop scan command is received from host.
•
No-read timer times out.
Chapter 7 provides a description of how to send start and stop trigger
commands from a host.
3) Internal Timer - If you select internal timer, the decoder will only decode
scan head data based upon the duration of the No-Read timer. The
No-read timer simulates the package detect input. When functioning as a
trigger source, the No-Read timer will alternate the trigger from ON to
OFF. The length of time the trigger is on and the trigger is off are equal
and is determined by the value entered in the No-Read timer field. Refer
to Figure 4.4.
Figure 4.4
Internal Timer Trigger
OFF ON ON
X Y
X = Y = No Read Timer Value in Milliseconds
Minimum Value = 10 msec
Maximum Value = 9995 msec
Count Increments in 5 msec intervals.
Note: When the decode trigger is not set to internal timer, the No-Read timer
functions as a trigger timeout. Once triggered by the host or package
detector, the decoder will decode bar code data until either the end of the
trigger or the No-Read timer times down to zero.
4) Continuous - If you select continuous decode triggering, the decoder will
continuously try to decode data received from the scan head.
Note: The No-Read condition does not exist in the continuous scanning
mode.