Rev. 01/2021
30
The PicoLAS Protocol
The following section describes the structure and possible commands of the PicoLAS
protocol.
Structure
Each transmission consists of 12 bytes – called a frame as follows – which must be sent
consecutively. Otherwise the system times out and the transmission must start again from the
beginning.
A frame has a fixed structure. The first two bytes describe the command, the following eight
bytes the parameters, followed by one reserved byte and one checksum byte. The checksum is
calculated out of the first 11 bytes which are linked by a bitwise XOR.
Thus a frame has the following structure:
Byte
Meaning
1
Bit 8-15 of the command
2
Bit 0-7 of the command
3
Bit 56-63 of the parameter
4
Bit 48-55 of the parameter
5
Bit 40-47 of the parameter
6
Bit 32-39 of the parameter
7
Bit 24-31 of the parameter
8
Bit 16-23 of the parameter
9
Bit 8-15 of the parameter
10
Bit 0-7 of the parameter
11
Reserved, always 0x00
12
Checksum
A properly received frame must be acknowledged by the recipient with an answer, which is
also a frame. If the acknowledgement does not occur the command has not been processed
and the sending procedure should be repeated.
If the recipient recognizes the command as valid, but not the parameters, it will answer with
an ILGLPARAM (0xFF12) as command.
In the case that the recipient receives an invalid command it will answer with UNCOM
(0xFF13).
If a faulty checksum is recognized the answer is RXERROR (0xFF10). If this error occurs
often the connection should be checked.
