User's Manual

Brooks Automation
54 260301 Revision A
7 Operation ATR60LF RFID Reader CAN Bus
7.5 Operation of the SECS Protocol Product Manual
The reverse bit (R bit) signifies the direction of a message. The R-bit
(msb) is set to 0 for messages to the equipment and to 1 for messages to
the host.
The W bit indicates that the sender of a primary message expects a reply. A
value of 1 in the W bit means that a reply is expected.
The message ID identifies the format and content of the message being
sent.
A primary message is defined as any odd-numbered message.
A secondary message is defined as any even-numbered message.
The end bit determines whether a block is the last block of the message. A
value of 1 means that the block is the last block.
A message sent as more than one block is called a multi-block message.
A block number of 1 is given to the first block, and the block number is
incremented by one for each subsequent block until the entire message is
sent.
As all messages can be sent in one block, the block number always has the
value
1.
The system bytes in the header of each message for a given device ID
must meet the following requirements:
 The system bytes of a primary message must be distinct from the
bytes of all currently open transactions initiated from the same
end of the communications link.
 The system bytes of the reply message are required to be the
same as the system bytes of the corresponding primary message.
The system bytes are incremented for each primary message.
The checksum is calculated as the numeric sum of the unsigned binary
values of all the bytes, after the length byte and before the checksum and
in a single block.