4. Configuration
191
Figure 4-92. Contrast Adjust
Besides the possibility of the Nexto CPUs menu to be closed through a long touch on the screen
diagnostic button RETURN from level 1, there are also other output conditions that are described
below:
ï‚· Short touch, at any moment, in the other modules existent on the bus, make the CPU disconnect
from the menu and show the desired module diagnostic
ï‚· Idle time, at any level, superior to 5 s.
Function Blocks and Functions
Special Function Blocks for Serial Interfaces
The special function blocks for serial interfaces make possible the local access (COM1 AND COM2)
and also access to remote serial ports (expansion modules). Therefore, the user can create his own
protocols and handle the serial ports as he wishes, following the IEC 61131-3 languages available in
the MasterTool IEC XE software. The blocks are available inside the Nexto Serial library which must
be added to the project so it’s possible to use them (to execute the library insertion procedure, see
MasterTool IEC XE Programming Manual – MP399608, chapter Library).
The special function blocks for serial interfaces can take several cycles (consecutives calls) to
complete the task execution. Sometimes a block can be completed in a single cycle, but in the general
case, needs several cycles. The task execution associated to a block can have many steps which some
depend on external events, that can be significantly delayed. The function block cannot implement
routines to occupy the time while waits for these events, because it would make the CPU busy. The
solution could be the creation of blocking function blocks, but this is not advisable because it would
increase the user application complexity, as normally, the multitask programming is not available.
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General