RTC
®
5 PC Interface Board
Rev. 1.9 e
6 Developing User Applications
69
innovators for industry
6.3 List Memory
List memory serves as intermediate storage for list
commands. Before list commands can be sent to the
RTC
®
5, a control command must define the input
pointer to which subsequent list commands will be
transferred (this corresponds to opening a list, see
commands start the processing of transferred list
commands.
6.3.1 Lists and the Protected Buffer
Area
The RTC
®
5’s list memory contains 1M
(= 1048576 = 2
20
) storage positions. The memory is
basically divided into three areas of variable (config-
urable) size:
• Two list buffers (“List 1” and “List 2”), later simply
referred to as “lists”
• A third “protected buffer area” (“List 3”), which is
protected against unintended overwriting during
loading of normal command lists
Lists
In principal, both list buffers (“List 1” and “List 2”)
can be used in a manner identical to the two list
buffers of the RTC
®
4, RTC
®
3 or RTC
®
2 PC interface
boards, e.g. for continuous loading and processing of
command lists.
But the RTC
®
5 provides significantly more memory,
and the size of each buffer area is freely configurable
(see
"Configuring the List Memory", page 70
).
Plus, the RTC
®
5 has enhanced command function-
ality for list handling, as detailed in
.
Protected Buffer Area
The third buffer area (“List 3”) – an RTC
®
5 innovation
– is a protected memory area intended for storing
frequently needed list-command sequences as
subroutines or character set definitions. This area is
protected against unintended overwriting during
loading of normal command lists.
There are principally two ways to utilize this
protection feature:
(1)
As with the RTC
®
5’s predecessors, subroutines
can be written to the upper positions of the list
buffers. What is new with the RTC
®
5 is that these
subroutines can be subsequently assigned to the
protected buffer area. Such subroutines are
called – both initially in the list-buffer area as well
as subsequently in the protected buffer area – via
specification of an absolute memory location.
(2)
Special commands allow subroutines and char-
acter set definitions to be loaded directly in the
protected buffer area as indexed subroutines or
definitions. They can then be called by providing
the corresponding index, thus potentially simpli-
fying later usage. Indexed character set defini-
tions can, for example, be used in conjunction
with the newly introduced
command
for directly marking text.
SCANLAB strongly recommends
not
intermixing
usage of these two methods. Otherwise, unintended
data loss via overwriting could occur even in the
protected buffer area.
The RTC
®
5 command set includes appropriate
conversion commands so that you won’t be forced to
continuously use only one of the two methods.
The defining of subroutines and character sets, as
well as their management and subsequent
conversion options are detailed in
.
