Rockwell Automation 2708-NBD VBASIC Language Development Kit - Manual (Page 21)

CROSS-COMPILER (LXB)
Chapter 3
The A-B VBASIC
3–4
B – Downloaded Executable File
The usual extension of a file that is produced by most other compilers is
“.OBJ”. Those files usually go through a separate LINK step before an
executable “.EXE” file is generated. However, the extension of the A-B
VBASIC cross compiler output is “.LXE”. The extension “.LXE” is used for
two reasons:
1. The file cannot be link edited like a usual PC object file.
2. There is only one useful operation that can be performed on this file:
Download it to a workstation.
The code portion of the file is checksummed. Except for carriage returns, the
entire file is within the printable ASCII character set. Transmission of a
download file using modems should be safe since a corrupted file will result
in a checksum error instead of program initiation.
C – Listing File
If specified, LXB places a listing into a file with the same base name as the
source file, with an “.LST” extension. The OFFSET column of the listing
shows the location of the pseudo-code corresponding to the BASIC
statement. Error messages at run-time provide this offset as an aid in locating
errors.
Program pseudo-code size is given in the listing file which can be used to
gauge how much of the maximum 13,700 bytes of available program space
(32K memory workstation) were used. Other statistics provide insight into
the free variable space and other elements of memory use.
D – Secondary Download File
If the secondary download file parameter is specified, then a .PGM file will
be output in addition to the .LXE file. The .PGM file is a special type of
download file which will not begin executing immediately, but rather stores
itself into RAM for future execution via a CHAIN statement from another
program. It does this by appending some additional network directives onto
the front of the file, and onto each record.
Invoking the Compiler
(cont’d)