Siemens SIMATIC Ident Function Manual page 42

Configuring the instructions
4.5 Programming instructions
There are four different modes that you can select with the "ATTRIBUTE" parameter.
• At the start, a certain duration/number (period of time, number of inventories, number
of "Observed" events or identified transponders) is specified. A distinction is made
between the following options:
– Duration
– Number of inventories
– Number of "Observed" events
Inventories are then taken by the reader for this time or number of inventories. When
the specified time/number is reached, the instruction is ended and returns all
identified transponders in "IDENT_DATA". In other words, other commands can only
be executed when all inventories have been taken completely. The unit (time or
number) is specified using "DUR_UNIT" and the value (time value or number) using
"DURATION". This mode can be executed using the attributes "0x80" and "0x81".
Depending on the attribute, more or less data is supplied about the identified
transponders.
• With the attributes "0x86" (start "Presence_Mode") and "0x87" (end
"Presence_Mode"), inventories can be taken permanently. The presence of a
transponder can then always be queried using "PRESENCE" without having to start
the "Inventory" instruction with "EXECUTE". No information about the identified
transponders is returned when the command executes!
To obtain information about the identified transponders, use one of the two calls
listed above (with time / number of inventories = 0).
When this mode is active, commands relating to transponders are not executed
immediately but only when a transponder is identified. This achieves shorter reaction
times since the command is already pending when the transponder enters the
antenna field.
"Presence_Mode" is practical in the context of the "Repeat command" function.
The "NUMBER_TAGS" output parameter is used to output the number of identified
transponders. With the attributes "0x80" and "0x81" on completion of the read operation,
the sum of all identified transponders is displayed. With the attribute "0x86" the number
of currently identified transponders is shown at the "NUMBER_TAGS" output parameter
(max. 15),without having to start the "Inventory" instruction with "EXECUTE".
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Take inventories for a specified period of time
Take a specified number of inventories
Take inventories until a specified number of transponders have been identified at
the same time.
Ident profile, Add-on instruction for Rockwell systems
Function Manual, 07/2020, C79000-G8976-C410-04