Rockwell Automation 57C610 Enhanced Basic Language, AutoMax - Manual (Page 68)

6Ć28
If the default setup or baud rate are not suitable for your application,
use the following OPEN statement format to temporarily allocate the
port for EXCLUSIVE access to change the default setup or baud
rate. This changes the default characteristics of the port until the
next power cycle or StopĆAllĆClear occurs. Use the CLOSE
statement to deĆallocate the port. The CLOSE statement must follow
the OPEN statement with no intervening INPUT, PRINT, GET or PUT
statements. The CLOSE statement must use the same device
number assigned in the OPEN statement.
OPEN PORTA" AS FILE #logical_device_number, SETUP=specs,
baud_rate \&
CLOSE #logical_device_number
Note: When an OPEN statement has a setup parameter, the port is
opened with EXCLUSIVE access. Therefore, specifying
ACCESS=NON_EXCLUSIVE causes a compile error to be logged. It
is not necessary to OPEN port A for NON_EXCLUSIVE access; this is
the default mode of operation. Do NOT use the device number
assigned in the OPEN statement to access the port in any
subsequent INPUT, PRINT, GET or PUT statements because the port
has been deĆallocated by the CLOSE statement above.
Examples:
INPUT INP%
INPUT:EMPTY=line_no, INP%
PRINT MSG$
GET CHAR$
GET:EMPTY=line_no, CHAR$
PUT CHAR$
Port A Ć Application Notes
1. Use port A instead of port B when port A is available because
the operating system manages port allocation and error
handling between tasks.
2. OPEN" the port to set required port characteristics, CLOSE"
the port, then use INPUT, PRINT, GET and PUT statements
without a device number in any task to access port A.
3. All tasks have only NON_EXCLUSIVE access to the port.
4. The port is opened and closed after each operation.
5. StopĆAllĆClear commands and power cycle close all ports. The
port characteristics are set to OS default. The user must set the
port to the required characteristics.
6. Stopping a task does not change the port setup and baud rate.
7. Errors logged to task information (for example, Framing,
Overrun, etc.) will have no major effect because the port is
opened and closed after each operation.
8. The serial port statements Print, Input, Put, and Get will operate
after an error has been logged because the port is opened and
closed after each operation.
Programming Example
The following example uses two tasks on the Processor to transmit
and receive data from port A. KYBD.BAS sets the characteristics for