Brooks LF80C - Page 84

Brooks Automation
72 278580 Revision A
7 Operation LF80C ZeniD RFID Reader
7.3 Operation of SECS Protocol Product Manual
HSMS message
header
The message header is a 10-byte field. The bytes in the header are
numbered from byte 0 (first byte transmitted) to byte 9. The format of the
message header is as follows:
The physical byte order is designed to correspond as closely as possible to
the SECS-I header.
The session ID is a 16-bit unsigned integer value, which occupies bytes 0
and 1 of the header (byte 0 is MSB). Its purpose is to provide an
association by reference between control messages and subsequent
messages.
Header byte 2 is used in different ways for different HSMS messages. For
control messages, it contains 0 or a status code. For a data message, it
contains the W bit and SECS stream.
Header byte 3 contains 0 or a status code for control messages. For data
messages, it contains the SECS function.
P-type is an 8-bit unsigned integer value which occupies byte 4 of the
message header; message header and message text are encoded. Only P-
type = 0 is defined by HSMS to mean SECS-II message encoding. For non-
zero P-type values, see SEMI E37.
S-type (session type) is a 1-byte unsigned integer value which occupies
header byte 5.
Bytes Description
0-1 Session ID (Device ID)
2Header byte 2
3Header byte 3
4P-type
5S-type
6-9 System bytes
Value Description
0 SECS-II Encoding
1 - 127 Reserved for subsidiary standards
128 - 255 Reserved, not used