Rockwell-automation 2708-NBD VBASIC Language Development Kit Manual de usuario descargar pdf (Pagina 34)

Chapter 4

Special Devices in A-B VBASIC

4–13

C – Modem Control Lines

The primary communication port is equipped with DTR and RTS. These can

be set through the IOCTL statements. The character string passed must

contain two bytes. There are two valid options for each byte:

“0” to turn the line off

“1” to turn the line on

The first byte controls DTR, the second controls RTS. Thus:

IOCTL #5, “01” turns off DTR and turns on RTS.

These modem lines can also be controlled using the BASIC Language

Development Kit routines SetDTR and SetRTS.

AUX has only one line, DTR. It is controlled in the same way as COM. For

future compatibility, always add a second (character) zero, to imply RTS off.

Name: Any name which is not reserved and is within the rules for file

names.

Description:

Data files on a PC are resident on disk. They are RAM resident in the

workstation. A-B VBASIC supports the three types of file access provided

with Visual BASIC, sequential, binary, and random. File I/O is thoroughly

discussed in Microsoft’s “Programming in BASIC, Chapter 3.

Statements and Functions supported:

①

CLOSE LOF

EOF OPEN

GET PRINT

INPUT$ PUT

KILL SEEK Statement

LINE INPUT SEEK function

LOC WRITE

CONST DataFile = 1

OPEN “EMPLOYEE” FOR OUTPUT AS #DataFile

PRINT #DataFile, “Employee ”;EmpName$ ;“ – ”;TIME$

CLOSE #DateFile

ATTENTION: Both Visual BASIC and A-B VBASIC allow a

PUT to a record number which is greater than the last record in

existence before the PUT. Both BASICs extend the file to the

length required to accommodate the request.

①

Refer to Appendix M for any restrictions on Syntax.

Devices: Communication

Ports, Primary and

Auxiliary (cont’d)

Device: RAM Files

1 2 ... 29 30 31 32 33 34 35 36 37 38 39 ... 83 84

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