Communications
MS-860 Industrial Raster Reader User’s Manual
6-13
Daisy Chain Mode
Usage:
Used in applications where:
• A symbol might be scanned in both ladder and picket fence directions.
• A bar code symbol may be present on multiple sides of a package.
• Bar code symbols are presented at different depths.
Definition:
In a daisy chain application, readers are connected in tandem or “daisy
chain” and decoded data is relayed from one reader to another on up to
the host.
A master reader has its host port linked to the host computer and its aux-
iliary port linked to the host port of the first secondary reader in the
chain. Thereafter, each secondary’s auxiliary port is linked to the host
port of the secondary that is further from the host in the daisy chain.
Each reader in the daisy chain can be assigned an ID that accompanies
any data that it sends.
Serial Cmd:
<
K101,aux port mode
,
baud rate,parity,stop bits,data bits,daisy chain
ID status,daisy chain ID>
Options:
4 = Daisy chain
Function:
Before the master reader times out, it checks its auxiliary port for data. It
should be set to wait at least
20
mS for each secondary in the daisy
chain. (See
"Read Cycle Timeout"
on page 7-15.) If no data is received
within the read cycle timeout, the master sends a noread message to the
host. Otherwise the complete data is sent.
If for example the master reader is set to timeout in 120mS, the first
secondary reader downstream might be set to 100mS, the next to 80mS,
and so forth, thus assuring that at least 20mS elapses between transmis-
sions.
a
Daisy-chained readers can send a series of symbols by enabling
Multi-
symbol and a common multisymbol separator. If the master reader does
not receive the expected number of symbols, noread messages are
appended to the data string to make up the difference between the num-
ber of symbols enabled in
Multisymbol and the number of symbols read.
For example, a master and two secondary readers have
Number of
Symbols set to 3 and Multisymbol Separator defined as %. If the
master and the first secondary reader do not find symbols, but the next
secondary reader registers a good read, the transmitted results would
be: symbol data % noread % noread.
a. The above example is based on the best case. Other factors such as baud rate, dynamic focus timing,
number of characters in a given symbol, and the number of secondaries in the daisy chain can
affect timing and may need to be included in your calculations for complete accuracy.
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