User Manual

CHAPTER 6: COMMAND PROTOCOLS
COBALT HF RFID CONTROLLERS OPERATOR’S MANUAL
P/N: 17-1320 REV 01 (03-06) PAGE 60 OF 116
CHAPTER 6:
COMMAND PROTOCOLS
6.1 COMMAND P ROTOCOL O VERVIEW
In order to correctly recognize and execute commands, the Cobalt HF and the host must
be able to communicate using the same language. The language that is used to
communicate is referred to as the Command Protocol.
There are two Command Protocols used by Cobalt HF RFID Controllers.
x ABx Fast Command Protocol
– for Point-to-Point, Host/Controller applications
(-232, -422 and –USB models).
x CBx Command Protocol
– for multiple RFID controller configurations, Multi-
drop (Subnet16) networks and Industrial Ethernet applications (-485 and –IND
models).
These two Command Protocols have different packet structures and parameter settings,
which are explained later in this chapter.
6.2 ABX F AST C OMMAND P ROTOCOL
The command protocol used by the Cobalt HF -232, -422 and -USB Controllers for Point-
to-Point data transmission is known as the ABx Fast Command Protocol. ABx Fast has
a single-byte oriented packet structure that permits the rapid execution of RFID
commands while requiring the transfer of a minimal number of bytes.
ABx Fast supports the inclusion of an optional checksum byte. By default, the HF-CNTL-
232, -422 and -USB controllers are configured to use ABx Fast without the checksum
option. However, when increased data integrity is required, the checksum should be
utilized. See Section 6.2.4 for more on using the checksum parameter.
6.2.1 ABx Fast - Command / Response Procedure
After an RFID command is issued by the host, a packet of data, called the “Command
Packet” is sent to the Cobalt Controller. The command packet contains information that
instructs the controller to perform a certain task.
The Cobalt Controller automatically parses the incoming data packet, searching for a
specific pair of start characters, known as the “Command Header.” (Note: in ABx Fast,
the Command Header / Start Characters are 0x02, 0x02). When a Command Header is
recognized, the controller then checks for proper formatting and the presence of a
Terminator byte. (Note: in ABx Fast, the Terminator byte is 0x03).
Having identified a valid command, the controller will attempt to execute the instructions,
after which it will generate a host-bound response message containing EITHER the
results of the attempted command or an error code if the operation failed.
All commands will generate a response from the controller. Before sending another
command, the host must first process (remove from memory) any pending response
data.