Rockwell-automation 2708-NBD VBASIC Language Development Kit Manual de usuario descargar pdf (Pagina 32)

Chapter 4

Special Devices in A-B VBASIC

4–11

IOCTL$ (intrinsic function) for HOST and NET

This function returns a string formatted as follows:

Byte 0: ‘0’ when the workstation is offline to the network.

‘1’ when the workstation is online.

Bytes 1-4: is the workstation’s number (without a minus).

Bytes 5-9: is the workstation type (its network role) as

NORML CONCN

MASTR SUBM

ALTM ALTSM

IOCTL (statement) for HOST

Characters 9 and 10 of all records arriving at the host contain a 2 digit

number (“Transaction Code”). Numbers 00, 98, and 99 are reserved. A-B

VBASIC programs can change these two digits for records from HOST, from

the default of 01.

For example, if the statement IOCTL #5, “29” is used where #5 is associated

with HOST, digits 9 and 10 of records containing data from this workstation,

will be 29.

Note: Only numeric digits are valid. IOCTL is not valid in its statement form

for the NET device.

Reserved device names: COM and AUX

Opening a com port:

Access to the communications ports begins with the statement OPEN

“COM” and OPEN “AUX”. On a PC, Visual BASIC allows you to specify

baud rate and other parameters in the OPEN “COM” statement. In A-B

VBASIC these are NOT valid! Comm parameters are set using the Setup

Menus (see Chapter 5 for details). If you are using the ENV/ENVPC

collections of subroutines in the BASIC Language Development Kit (Catalog

No. 2708-NBD), a call to OpenLINX will automatically open all required

comm ports.

The primary communication port is dedicated to networking functions in all

terminal types except NORMAL. Any attempt to OPEN

’COM” on any workstation which has not been set to a workstation type of

NORMAL (using the Setup Menus) will result in a runtime error.

Units with a second (“AUX”) port may use that port via OPEN “AUX”

regardless of the workstation‘s network role.

OPENing a communications port has no effect on the state of the modem

control lines DTR and RTS. These are always under the control of the

BASIC program using IOCTL, or one of the BASIC Language Development

Kit subroutines discussed later.

Details of Specific Statements

and Functions (cont’d)

Devices: Communication

Ports, Primary and

Auxiliary

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