Rockwell-automation 2708-NBD VBASIC Language Development Kit Manual de usuario descargar pdf (Pagina 25)

Chapter 4

Special Devices in A-B VBASIC

4–4

Reserved device name: BAR

Open Modes: INPUT

Statements: LINE INPUT

Functions: EOF returns TRUE when a complete record has

arrived. Once TRUE, a LINE INPUT statement

can be used and will immediately return the data

when LINE INPUT completes. EOF returns to

FALSE.

LOF remains 0 until a barcode is read. Then it

contains the length of the data record. It must be

called before LINE INPUT. Once LINE INPUT

has been used, LOF returns 0 until the next

barcode is read.

IOCTL$ may be called after LINE INPUT to obtain more information about

the type and origin of the data. In general, the string which is returned is of

the form:

Type/Source

When reading barcodes:

Type can be: C39, I25, UPC, CBAR, or C128

Source can be WAND or LASER

There are two intrinsic functions which may be used before LINE INPUT to

determine whether a barcode has been read: EOF, and LOF.

For barcodes, “read” means that the operator correctly used a wand, laser, or

slot reader to scan one of the barcode types enabled through the barcode

menu. For example, an A-B VBASIC program will not be aware that a UPC

barcode has been scanned if UPC is not enabled or if another condition such

as a check digit has not been satisfied. It also means that the operating

system was able to decode the pattern of the barcode because the reader was

operated at the correct speed and angle. Unsuccessful attempts to read a

barcode are not reported to the BASIC program.

Once a read has occurred, the TRUE returned by EOF, the barcode length

from LOF, and the data from LINE INPUT, are “latched” until a LINE

INPUT is used.

Note: Allen-Bradley slot scanners (Catalog No. 2755-B1, -B2) can be used

in place of a wand or hand-held scanner.

Device: Barcode Scanners

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Rockwell-automation 2708-NBD VBASIC Language Development Kit Manual de usuario Pagina 25