ThingMagic Mercury6e M6e-30dBm, Hardware Manual

Page: 34 / 78

Serial Communication Protocol
34
Communication Protocol
Serial Communication Protocol
The serial communication between a computer (host) and the M6e 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 must manage retries, if
necessary. The host must keep 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 250 bytes 2 bytes