Advantech AWMT, Инструкция по установке и эксплуатации

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AWMT
42
10. APPENDIX A: RS-485 SERIAL COMMUNICATION PROTOCOL
The protocol described in this Section is used for the interconnection between the AWMT and
the user’s monitoring and control system. The protocol supports the 4-wire RS-485 interface
using the communication set-up 9600.N.8.1.
10.1 FRAME STRUCTURE
Each frame starts from start byte – 0x55
After this start byte, each frame consists of 7 bytes described as follows:
•
First byte master–slave – address of the correspondent unit (0x01 to 0x07, address 0x00 –
will be used as broadcast address and must be used only for commands.
•
First byte slave-master – address of the unit, shifted to the left by 4 (e.g. for a unit with
address 0x05, the returned address is 0x50).
•
Second byte master-slave – command or data request.
•
Third, forth and fifth bytes master-slave – value of parameter or expansion of command:
third byte – MS byte, forth byte – LS byte, fifth byte – value after decimal point.
•
From second to sixth bytes slave-master – data or status from slave.
•
Seventh byte master-slave and slave-master - check sum, calculated as algebraic sum of bytes
1-6.
NOTE: Format for gain, level, current consumption and temperature is a 2-byte
hexadecimal value in 0.1 dB, 0.1 dBm, 0.1 A or 0.1 degree (signed integer).
Format for the LNX current is a 2-byte hexadecimal value in 1 mA steps
(unsigned integer).
Format for frequency is a 2-byte hexadecimal value in 1 MHz steps (unsigned
integer). All unused bytes are always - 0xAA.
10.2 COMMANDS
TABLE 11 at page 43 lists all of the commands that go in the master-slave direction.
NOTE: If slave does not recognise the command from the master, the response of the
slave is given in
TABLE 12 at page 44.