Brooks Automation
66
278580 Revision A
7 Operation
LF80C ZeniD RFID Reader
7.3 Operation of SECS Protocol
Product Manual
Direction reader to host
0x81xx *
Direction Host to equipment (reader) 0x01xx *
* The serial number is located on a label on the reader.
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.
Block transfer
protocol
The drawing below illustrates some simple message interactions between
the host and the equipment. The figure shows the possible handshake
sequence to acquire the status of the equipment.
When the host wants to send, it first sends an
<ENQ>
and then tries to
read.
If it receives an
<EOT>
, it sends its message and then expects an
<ACK>
.
Upper device ID
R-bit 0 0 0 0 0 0 1
Lower device ID
Last two digits of the serial
number
