INFICON HLD6000 Refrigerant Leak Detector Interface Description - Manual (Page 16)

16 LD Protocol
3 LD Protocol
3.1 Communication Parameters
3.2 Command Format
3.2.1 Telegram Structure
Master sends
Slave answers
Data format
Baudrate 19.200, 8 data bits, 1 stop bit, no parity
ENQ LEN ADR CmdH CmdL DATA (n bytes) CRC
0 1 2 3 4 5 5 + n
STX LEN StwH StwL CmdH CmdL DATA (n bytes) CRC
0 1 2 3 4 5 6 6 + n
Command Meaning
ENQ 0x05 Start of master request
STX 0x02 Start of slave response
LEN Number of telegram
bytes without ENQ(STX)/LEN, however with CRC
max. 253, so the total slave telegram length
is max. 255
ADR Slave address Slave address = 1: non-addressed bus.
Address byte is ignored.
Stw H/L Status word Info from slave to master. Please use
ADR=1 only.
Concerning status
see page 19 .
Cmd H/L Command Bit 15 ... 13: Command-specifier Read/
Write etc. (see table “
Cmd H/L: Command:
Command-specifier ”)
Bit 12: free
Bit 11 ... 0: Command (
see page 20 )