ThingMagic M5e-Compact - Manual (Page 53)

Overview of the Communication Protocol 53
Overview of the Communication
Protocol
The serial communication between a computer (host) and the reader is based on a
synchronized command-response/master-slave mechanism. Whenever the host sends a
message to the reader, it cannot send another message until after it receives a response.
The reader never initiates a communication session; only the host initiates a
communication session.
This protocol allows for each command to have its own timeout because some
commands require more time to execute than others. The host manages retries, if
necessary. The host keeps track of the state of the intended reader if it reissues a
command.
Host-to-Reader Communication
Host-to-reader communication is packetized according to the following diagram. The
reader can only accept one command at a time, and commands are executed serially, so
the host waits for a reader-to-host response before issuing another host-to-reader
command packet.
Header Data Length Command Data CRC-16 Checksum
Hdr Len Cmd CRC Hi CRC LO I
1 byte 1 byte 1 byte 0 to N bytes 2 bytes