ABB_800xA学习笔记245:System_800xA_Control_6.0_AC_800M_Configuration35

标签:
abbsystem_800xa_ac800m配置手册功能和组件 |
分类: ABBDCS |
继续学习配置手册第一章功能和组件,进入第93页。
The following example tries to
illustrate how a variable will be handled,
depending on
different attribute settings. Suppose the variable valveC has the
attribute coldretain, valveR has the attribute retain and
valve has no attribute. Also,
suppose that these three variables have the initial
value = True (see Figure 28 for the
variable declaration).
下面的示例尝试说明如何处理变量,具体取决于不同的属性设置。假设变量
valveC 具有 coldretain 属性,valveR 具有 retain 属性,而 valve
没有属性。此外,假设这三个变量的初始值 = True(有关变量声明,请参见图28)。
Figure 28. Three variables with
different attributes settings
图28. 三个设置不同属性的变量
According to the attribute settings
in Figure 28, the variables will be read or
written on
different occasions in the given code example below, (read the
comments under each IF statement):
一句图28设置的属性,变量在不同情况下进行读写(阅读每个if语句下面的注释)。
IF valveC THEN
(*Code in this
position is only executed once after the very
first cold
restart*)
valveC :=
false;
END_IF
IF valveR
THEN
(*Code in this
position is only executed once after a cold
restart*)
valveR :=
false;
END_IF
IF valve
THEN
(*Code in this
position is only executed once after a cold restart
and once after a
warm restart*)
valve :=
false;
END_IF
Note that execution does not have to
take place during the first scan after restart,
for example, when
IF valve is embedded in another IF statement.
请注意,在重新启动后的第一次扫描期间不必执行,例如,当 IF
阀嵌入到另一个 IF 语句中时。
Variables and parameters should have
the attribute retain, unless they are written
at each scan. When
a change has been made to the application, the entire
application will be (warm) restarted and in doing so,
variables without the attribute retain
will be set
to their initial values, and there is a chance that the change will
not be totally bumpless. It is recommended that In and Out
parameters to function blocks
always have
the attribute retain.
变量和参数应有属性值retain,除非每一次扫描时写入它们。当对应用程序修改时,整个应用程序将热启动,在此过程中,没有保持属性的变量将设置为初始值,并且更改可能不会完全没有震荡。建议始终将功能块的In和Out参数设置retain属性。
More
information is given in Control Builder online help. Search the
index for “attribute”.
Control Builder
联机帮助中提供了更多信息。在索引中搜索“attribute”。
Initial Values
初始值
It
is possible to give the variable an initial value, which will be
assigned to the variable the first time the application is
executed. This setting overrides the
default data type value. Table 6 shows default initial
values for the most common
data types.
可以为变量指定一个初始值,该值将在第一次执行应用程序时分配给变量。此设置将覆盖默认数据类型值。表
6 显示了最常见数据类型的默认初始值。
Descriptions
描述
The
description field describes and provides information about the
variable. A short descriptive text may include an explanation of
the cause of a condition or a
simple event, for example “Pump 1 is running”. Since
the description is not downloaded
to the
controller, the size of the description is
irrelevant.
description
字段描述并提供有关变量的信息。简短的描述性文本可以包括对条件或简单事件原因的解释,例如“泵 1
正在运行”。由于描述不会下载到控制器,因此描述的大小无关紧要。