Siemens SIMATIC Ident RF200 Operating Manual page 20

Command and message frames
2.10 "ANW-MELD" message
Address
Byte 6
Byte 7
Byte 8
Byte 9
With the active presence check, if there is a change in the presence status, the reader sends
a frame with the number of transponders in the antenna field. If a transponder leaves the
field at the same time as another transponder enters the field, two "ANW-MELD" messages
are sent.
Note
Reachability of the host
The presence message is asynchronous (i.e. without a request from the host).
This means that the host must always be ready to receive and must make suitable buffers
available so that the message can be processed immediately.
20
Designation
reserved
Presence status
Value
0x30
0x30
0x30
0x30 / 0x31
Operating Manual, 11/2016, C79000-G8976-C329-04
Description
--
0x30 ≙ no transponder in the an-
tenna field
0x31 ≙ one transponder in the
antenna field
ASCII protocol for RF200