User manual

C - 54 Magelis
4. Dialog table
The display unit reads and writes the table in the PLC.
On power-up or restarting communication, the display unit reads the
command table and writes the status table.
In the event of a problem, the display unit informs the user with a
message.
NOTE: The "Authorization" word is used as a safety measure for the PLC.
In fact, when this word has the incorrect value in the PLC, the
display unit does not write any dialog table words to the PLC.
Nor will it interpret the command words in the dialog table.
 Exchanged data
The dialog table is accessed cyclically in two phases: first a read phase,
then a write phase. A few notorious exceptions should be pointed out, for
example the images of the function keys or the images of the keypad
keys, which are updated immediately.
It is also important to note functions are processed in the order in which
they are stored in the dialog table, for either reading or writing: The
function read first is the first to be processed, and the function written first
is the first to have been processed (except for key images).
The structure of a table is always as follows:
->, <->, <- : Direction of communication
From the viewpoint of the display unit, on each cycle there is:
1) A read phase: Blocks 2 and 3 are retrieved
2) A write phase: Blocks 1 and 2 are updated if necessary
Block 1 Part containing the XBT -> PLC words
Block 2 Part containing the XBT <-> PLC words
Block 3 Part containing the XBT <- PLC words
XBT ref. Note
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