Microscan MS-820 Manual de usuario descargar pdf (Pagina 34)

Auxiliary Port

2-10 MS-820 Industrial Bar Code Scanner User’s Manual

2–Communications

Daisy Chain Mode

Note: See also “Daisy Chain Autoconfigure” on page 2-27.

Definition: In a daisy chain application, scanners are connected in tandem or

“daisy chain” and decoded data is relayed from one scanner to another

on up to the host.

A master scanner has its host port linked to the host computer and its

auxiliary port linked to the host port of the first “slave” scanner in the

chain. Thereafter, each slave’s auxiliary port is linked to the host port of

the slave that is further from the host in the daisy chain.

Each scanner in the daisy chain can be assigned an ID that accompa-

nies any data that it sends.

Usage: Useful in applications where:

• A bar code label might be scanned in both ladder and picket fence direc-

tions.

• A bar code label may be present on multiple sides of a package.

• Bar code labels are presented at different depths.

Serial Cmd: <Kyaux port mode,baud rate,parity,stop bits,data bits,daisy chain ID

status,daisy chain ID>

Options: 4 = Daisy chain

Function: Before the master scanner times out, it checks its auxiliary port for

data. It should be set to wait at least 20 mS for each slave in the daisy

chain. 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 scanner is set to timeout in 120 ms, the first

slave scanner downstream might be set to 100 ms, the next to 80 ms,

and so forth, thus assuring that at least 20 mS elapses between trans-

missions.

Daisy-chained scanners can send a series of labels by enabling Multila-

bel and a common multilabel separator. If the master scanner does not

receive the expected number of labels, noread messages are appended

to the data string to make up the difference between the number of

labels enabled in Multilabel and the number of labels read.

For example, a master and two slave scanners have Number of Labels set

to 3 and Multilabel Separator defined as %. If the master and the first

slave scanner do not find labels, but the next slave scanner registers a good

read, the transmitted results would be: label data % noread % noread.

a. The above example is based on the best case. Other factors such as baud rate, number of characters in

a given symbol, and the number of slaves in the daisy chain can affect timing and may need to be

included in your calculations for complete accuracy.

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Microscan MS-820 Manual de usuario Pagina 34

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