Methods Of Operation With The Communications Module - Siemens SIMATIC Ident Function Manual

B.3

Methods of operation with the communications module

Commands are executed one at a time
This means that, after each command, the user must wait for the acknowledgment (result)
before the next command is sent to the CM. This type of programming involves the following
characteristics.
● Simple function block programming
● No optimal-speed data transmission for several consecutive commands
The following diagram shows the sequence of the command and acknowledgement
exchange between user (PROFINET/PROFIBUS master) and CM.
RFID command execution
Figure B-6
Command chaining and buffering on the CM
Command chaining is indicated when the chaining bit (bit 6 in the command) is set (see also
the section "RFID commands (Page 29)").
Command buffering is a characteristic of the CM or the reader. A variety of buffers are
available to the CM/reader for intermediate storage of commands and results.
Use of command chaining and command buffering involves the following properties:
● Programming a function block becomes more complex.
● Optimum data throughput to and from the tag.
FB 45 for MOBY U, MOBY D, RF200, RF300
Function Manual, 07/2012, J31069-D0166-U001-A4-7618
Command execution: one command at a time
This is particularly noticeable with large amounts of data (> 1 KB) and slower PROFIBUS
transmission rates.
Programming communications modules
B.3 Methods of operation with the communications module
105