RTC
®
5 PC Interface Board
Rev. 1.9 e
10 Commands And Functions
337
Parameters
ListNo
Number of the list in which the input pointer should be set, as an unsigned
32-bit value; permissible values: [0 … 3]; only the two least significant bits are
evaluated.
=1: “List 1” will be opened if not BUSY (BUSY1 status not set).
=2: “List 2” will be opened if not BUSY (BUSY2 status not set).
=0: The list that is currently not BUSY will be opened. If both lists are not BUSY, then “List 1” will
be opened.
=3: The list that is currently not BUSY but USED (USED status set) will be opened. If both lists are
not BUSY and both are USED, then that list will be opened, which would be executed by a
following automatic list change.
For Mem2 = 0 (see config_list) “List 1” will be opened if not BUSY (ListNo = 0…2) or if not BUSY
but USED (ListNo = 3).
Pos
Position of the input pointer (offset relative to the start of the respective list)
as an unsigned 32-bit value; permissible range: [0 … (2
20
–1)]
Result Number of the opened list [1 or 2] if successful, otherwise 0
(as an unsigned 32-bit value)
Comments • The load_list command (
ListNo
= 3) is useful in scenarios such as alternating list
changes, where you want to wait specifically for a list to be processed (see "Alternating
List Changes", page 75) without needing to separately query the list status. Uninten-
tional overwriting of not-yet-executed commands is thereby automatically avoided. To
instead perform unconditional loading, you can use commands such as
set_start_list_pos.
• After a successful check of the list number (BUSY status not set and, if applicable, USED
status set), the load_list command behaves like set_start_list_pos (see comments
there).
•If the load_list command was not successful (return code 0), then no list will be opened
and the input pointer will be set to an invalid position. Then no further list commands
can be input until the input pointer is correctly set (e.g. by repeating the load_list
command with a positive result or via the set_start_list_pos command etc.). It is up to
the user to react to a return code of 0. The load_list command produces no wait loop
and doesn’t block execution of subsequent control commands.
•If
ListNo
= 0…2 when using the load_list command, then note that a list’s BUSY status
can change between opening of the list with load_list and the actual loading of list
commands, e.g. if in the meantime an automatic list change has occurred that was
previously defined via auto_change or start_loop. In cases such as this, where loading
of a list might occur simultaneously with processing of the same list, the user must
always ensure that the output pointer does not overtake the input pointer.
• In contrast, for
ListNo
= 3 load_list ensures that a list is actually opened for loading
only directly after processing (and after any successful automatic list changes). Particu-
larly, if no list is BUSY and both lists are USED (e.g. after initialization, after
stop_execution or after an external list stop), the opened list number is synchronized
with the following automatic list change.
RTC
®
4
RTC
®
5new command
References set_start_list_pos
Ctrl Command load_list
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