Rockwell Automation 2708-DH5B2L_DH5B4L Attended Workstation - Manual (Page 100)

Chapter 12
Special Devices in A-B VBASIC
12–4
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: Code 3 of 9, 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