Rockwell Automation 57C610 Enhanced Basic Language, AutoMax - Manual (Page 70)

6Ć30
Configuring and Using PORT B
For port B, you must use the OPEN statement in a task to allocate
the port before the task can communicate through the port, even if
the default port setup and baud rate are acceptable for your
application.
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 PORTB" 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. A
second OPEN statement must be added after the port is closed as
shown below.
If the default or configured port setup and baud rate are proper for
your application, use the following OPEN statement format to
allocate the port for NON_EXCLUSIVE access so the task can
communicate through the port. The port must remain open to
execute subsequent INPUT, PRINT, GET, or PUT statements.
OPEN PORTB" AS FILE #logical_device_number,
ACCESS=NON_EXCLUSIVE
The format of the INPUT, PRINT, GET, or PUT statements used to
communicate through the port is INPUT #, PRINT #, GET # or PUT
#, where # is the device number assigned to the port in the OPEN
statement. Whenever you refer to the port in subsequent
statements, always use the device number assigned to the port in
the OPEN statement.
In addition, if you want to make the port accessible to multiple tasks
in the Processor at the same time, you must add an OPEN
statement with the ACCESS parameter specified as
NON_EXCLUSIVE in each task that must communicate through the
port using the same logical_device_number that was used to identify
the port in the first task.
You must add software interlocking to each task attempting to
allocate the port to ensure that the task can determine whether the
port setup and baud rate have been initialized prior to opening the
port for NON_EXCLUSIVE access. Only one task needs to allocate
the port and define the setup and baud rate initially. Software
interlocking is also needed for port error handling. Tasks may need
to close and reĆopen the port on error conditions.