User's Manual

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Proprietary and Confidential Revised 10-11-11
SXL1 Serial Message Protocol
The SXL1 uses the on board RF transceiver and the programmer for both configuration and support
of wireless sensors. The SXL1 programmer can accept serial commands from a sensor or it can be
connected directly to a open/closed or analog sensor. This user’s manual contains the messaging for
serial wireless sensors only. When the programmer is connected to an open/closed or analog sensor
it uses the following protocol to send the appropriate message to the SXL1 for transmission.
Serial Protocol
The SXL1 may be configured using USB commands via the configuration connector. The SXL1
accepts USB serial logic levels between 0 to 5.0V DC. The interfacing connectivity provides voltage
and inrush protection for the interface.
The serial protocol conforms to the following general format. Each message starts with a preamble
byte followed by a length byte followed by a serial command designator, payload and concludes with
a two-byte CRC.
Preamble
(1 byte)
Cmd
(1byte)
Data
(Variable)
5 to 54 bytes
Length
(1 byte)
CRC
(2bytes)
Serial Set Format (Commands & Answers)
The different fields are defined as:
Serial Packet Fields
Position Bytes
Preamble Fixed pattern 0xAA
Length Total number of bytes in the serial et including the preamble
Cmd Command type (See section 3.2 below). Responses to commands
carry the same command type as the command that initiated the
answer
Data Data associated with the command or answer
CRC low Least significant byte of the 16-bit CRC
CRC high Most significant byte of the 16-bit CRC