RTC
®
5 PC Interface Board
Rev. 1.9 e
6 Developing User Applications
72
Loading with Protection
The loading process is initialized via the command
load_list, which sets the input pointer to the
specified address in the selected list (just like the
set_start_list_pos command), but only if the
selected list is not currently in use. Alternatively, you
can simply let the input pointer be set to a currently
non-active or already processed list via load_list (the
RTC
®
5 will automatically determine the corre-
sponding appropriate list).
The return value of the load_list command reveals if,
and in which list, the loading procedure was success-
fully initialized. Otherwise, the input pointer will be
set to an invalid position, in which case 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).
This automatically prevents unintentional over-
writing of not-yet-executed commands.
The load_list command 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).
Terminating Lists
Command lists can be, but need not necessarily be,
terminated via the set_end_of_list command.
However, if an unterminated command list is
executed and the output pointer thereby encounters
the last possible position in the list, the output
pointer will automatically reset to the start of the list
and processing will continue there. Automatic list
changing after a list is processed can only occur if the
list was terminated via the set_end_of_list command
(see "Automatic List Changing", page 75).
The loading of a set_end_of_list command will not
stop the loading procedure itself. Additional
commands in the same command list can be further
loaded directly after the set_end_of_list command.
6.4.2 List Status
Dependent on the command input and output
statuses, lists can receive particular status values. To
examine the current statuses of the lists, the control
command read_status (page 390) can be used –
separately for both lists.
• A list’s LOAD status (LOAD1 or LOAD2) indicates
that the input pointer is currently in this list. The
LOAD statuses of the other lists are then not set.
• A list’s READY status (READY1 or READY2) is set
when the set_end_of_list command is written
during the loading procedure. It is reset when the
list’s LOAD status is newly set.
• A list’s BUSY (BUSY1 or BUSY2) status indicates
that the output pointer is currently in this list
after list execution (of “List 1” or “List 2”) was
started. The BUSY statuses of the other lists are
then not set. Execution of the set_end_of_list
command causes a reset of the BUSY status (or
alternating setting, if automatic list changing was
previously activated). If a list is opened for
loading while still being processed, its BUSY
status will still remain set.
• A list’s USED status (USED1 or USED2) is set when
the set_end_of_list command is reached during
processing. It is reset when the list’s LOAD status
is set.
Notes
• If the list status is queried during processing of a
subroutine in the protected buffer area (“List 3”),
then the status will be returned of the list (“List 1”
or “List 2”) in which the output pointer most
recently resided (typically from where the
subroutine was originally called).
• If list execution is interrupted (via pause_list,
stop_list or set_wait), then the above-
mentioned status values will remain unchanged.
• If list execution is aborted (via stop_execution or
an external list stop), the USED status is set for
both lists (as via initialization). Also see
load_list(
ListNo
=3).
• If you want to explicitly set the USED status for a
list
ListNo
(e.g. after abortion via
stop_execution or an external list stop), then
load a set_end_of_list command to a free
position Pos of this list via
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