Presence Check; No Tag Control, No Presence Check: Mds_Control = 0; No Tag Control, Presence Control With Field Scanning: Mds_Control = 1 - Siemens SIMATIC Ident Function Manual

Parameterizing

3.3 Presence check

3.3 Presence check
This section explains the mechanism of the presence check. As default, the CM or the
reader operates with the presence check.
Presence check
The presence check is detection logic in the firmware of the reader that detects whether or
not a mobile data memory is currently located in the area of the reader. It can be controlled
with various mechanisms. Selection is carried out using the parameter MDS_control.
Currently the mechanism "with field scanning" is available with the MDS_control = 1
parameter.
Field scanning (MDS_control = 1):
The reader's firmware continuously scans its surroundings via the magnetic field to
determine whether a transponder is present. A hysteresis during field scanning suppresses
most of the switching back and forth of ANZ_MDS_present when a tag stops at the border of
the field.
Presence
A transponder is currently within the operating range of the reader. The presence bit
(ANZ_MDS_present in the command and status word) is set (see section "Command and
status word (Page 26)"). The presence display is indicated by the PRE LED on the front of
the communications module (see section Brief description of the hardware (Page 81)). Some
of the readers have their own LEDs and display responses that can be found in the relevant
manual.
3.3.1

No tag control, no presence check: MDS_control = 0

The message about the presence of a tag is suppressed by the ANZ_MDS_present variable.
3.3.2

No tag control, presence control with field scanning: MDS_control = 1

In this mode, the field of the selected reader is always on. As soon as a tag moves into the
field of the reader, this is indicated to the user via the ANZ_MDS_present bit (see section
"Command and status word (Page 26)"). The user can then start a command at any time. No
error message is generated if the tag leaves the field during processing.
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FB 45 for MOBY U, MOBY D, RF200, RF300
Function Manual, 07/2012, J31069-D0166-U001-A4-7618