Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 59)

Chapter 4
Configuring Your Decoder
4–32
numeric value from 1 through 8. This parameter must be met for a “Read“ to
occur (see Output section later in this chapter).
NO-READ TIMER (Milliseconds) (r) - This timer determines a no-read
condition when the decoder is in a triggered mode. After receiving a trigger,
the no-read timer will begin to time out. If a “Read“ (satisfying the
fields/package requirements) does not occur before the timer times out, a
No-Read condition will occur. The No-Read timer must be long enough to
allow the entire package to be read, otherwise a no-read will occur. The
no-read timer can also function as a trigger source when the decode trigger is
set to internal timer (refer to the description of the Decode Trigger Mode
field). You must enter either a numeric value from 10 through 9999 or a
value of 0 which disables the timer.
Note: The timers (No-Read & Inter-Scan) have an accuracy of
±
5
milliseconds.
INTER-SCAN TIMER (Milliseconds) (s) - This field sets the allotted time
between a valid read and the beginning of the next scan in which decoding
can be attempted.
You should use the inter-scan timer in applications where you need to
discriminate between multiple bar code fields appearing on the same label
(on different scans) and you cannot ensure the uniqueness of the bar code
fields. The first valid scan starts the inter-scan timer. The decoder cannot
decode another scan until the inter-scan timer times out. You can use the
inter-scan timer in both continuous or triggered scanning modes. You must
enter either a numeric value from 10 through 9999 or a value of 0 which
disables the timer. You should set the timer so that after a valid scan, the
attempt to decode the next scan is started between the bar code fields (see
next page).
After the decoder decodes the first scan, a second scan is not recognized until
a scan is decoded that is different from the first. The third bar code scanned
must be different from the second, etc.
Note: When using both the no-read and inter-scan timers, make sure that
your no-read timer is set to a value greater than the value entered for the
inter-scan timer so that all labels on the package are read before the No-Read
timer times out.
Note: Automotive Industry Action Group (AIAG) labels contain unique bar
code fields. Therefore, we recommend that you disable the inter-scan timer
when scanning AIAG labels.
Note: If continuous decode triggering is selected and the same bar code field
is decoded continuously, the inter-scan timer will effectively determine the
rate at which the decoded data is sent to the HOST port, AUX port, or used
for match code operation.