Brooks Automation
278580 Revision A
65
LF80C ZeniD RFID Reader
7 Operation
Product Manual
7.3 Operation of SECS Protocol
Message block
structure
SECS message blocks have the following form:
The operation of all communication functions above the block transfer
protocol is linked in information contained in a 10-byte data element, called
the header.
The header is always the first 10 bytes of every block sent by the block
transfer protocol.
The
length
includes all bytes sent after the length byte, excluding the two
checksum bytes. The maximum block length allowed by SECS-I is 254
bytes and the minimum is 10 bytes.
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
device ID
is a definite number to contact the reader.
The device ID consists of the 8-bit gateway ID (bit 0 - bit 7), which is
identical with the last two characters of the reader's serial number, and a 5-
bit fixed reader number
(bit 8 - bit 14 = 0x01).
Of course, the ID can be changed within the valid scope.
Byte
msb
Description
Length
0
Length without checksum, 10 - 254
Header
1
R
Upper device ID (Reader ID)
2
Lower device ID (Gateway ID)
3
W
Upper message ID (Stream)
4
Lower message ID (Function)
5
E
Upper block number
6
Lower block number
System
bytes
7
System byte 1
8
System byte 2
9
System byte 3
10
System byte 4
Text
11 - 254
Message text, user data
Checksum
255, 256
16-bit unsigned checksum
