The following table explains variables, addresses and tags.
|
Terminology |
Definition |
|
Internal memory |
The memory space in the target panel that can be
accessed by the panel application. For example, the user
memory $U, the non-volatile memory $N, the system memory
$S, and the recipe memory $R are all parts of the
internal memory. |
|
Internal variable |
An address or a tag referring to an address of a space
in the internal memory. |
|
Internal bit variable |
An internal variable that refers to a bit in the
internal memory.
Note: "Internal
variable" instead of "internal bit variable" is used
when referring to a bit if there is no ambiguity. |
|
Internal word variable |
An internal variable that refers to a word in the
internal memory.
The variables can also be used to refer to a
double-word, a block of bytes (byte array), a block of
words (word array), and a block of double-words
(double-word array).
Note: "Internal variable"
instead of "internal bit variable" is used when
referring to a bit if there is no ambiguity. |
|
External memory |
The memory spaces or the collections of addressable
devices in the controllers that can be accessed by the
panel application through communication links. |
|
External variable |
An address or a tag referring to an address of a space
in the external memory. |
|
External bit variable |
An external variable that refers to a bit in the
external memory.
Note: "External variable"
instead of "external bit variable" is used when
referring to a bit if there is no ambiguity. |
|
External word variable |
An external variable that refers to a word in the
external memory.
The variables can also be used to refer to a
double-word, a block of bytes (byte array), a block of
words (word array), and a block of double-words
(double-word array) if the access unit of the associated
addresses is word. If the access unit is double-word,
you can only use the variable to refer to a double-word
or a block of memory space with a length of a multiple
of 4 (bytes).
Note: "External variable"
instead of "external bit variable" is used when
referring to a bit if there is no ambiguity. |
|
External byte variable |
An external variable that refers to a byte in the
external memory.
Note: You can only use the
variable if the access unit of the associated addresses
is byte. |
|
Variable |
An internal variable or an external variable. |
|
Bit variable |
An internal bit variable or an external bit variable. |
|
Word variable |
An internal word variable or an external word variable. |
|
Byte variable |
An external byte variable. |
|
Double-word variable |
An internal variable or an external variable that refers
to a double-word. |
|
Byte array variable |
An internal variable or an external variable that refers
to a byte array. |
|
Word array variable |
An internal variable or an external variable that refers
to a word array. |
|
Double-word array variable |
An internal variable or an external variable that refers
to a double-word array. |
|
Tag |
A name that stands for an address of the internal memory
or the external memory. It also specifies the data type
and scan rate of the data in the memory location it
refers to. |
Note: Byte access is supported for the following PLCs:
1) Simatic S7-200 (PPI; 1-to-1)
2) Simatic S7-300 (MPI Port)
3) Simatic S7-300 Ethernet Module (CP343)
4) Simatic S7 (Ethernet)
5) S7-200 SMART (Ethernet)
6) VIPA 100V/200V MPI Port
Source.Section 4.4.3.1 of the PM Designer Software User Manual, Edition 2.0, © Cermate Technologies Inc. (www.cermate.com, service@cermate.com). Reproduced online, with the manual's own figures, by TSL Automation Solutions, authorised Cermate distributor, for users of Cermate HMI panels. PM Designer and PanelMaster are trademarks of Cermate Technologies Inc.
Text and figures are the manufacturer's and may describe features your panel or software version does not have. For a plain-language introduction read the PM Designer guide; for help with a specific panel contact TSL Automation.
