Advantech SSPB-3000C, Инструкция по установке и эксплуатации, Страница: 42 / 55

SSBP-3000C
Page 41
9. RS-485 SERIAL COMMUNICATION PROTOCOL
The protocol described in this Section is used for the interconnection between the SSPB Block
Up-Converter unit 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. This protocol is fully compatible to
Sierra Com protocol.
9.1 FRAME STRUCTURE
Each frame begins with the same starting byte: 0x55.
After the starting byte, 7 bytes are following.
The first byte in the master-to-slave direction is the address of the correspondent unit (0x01 to
0x07; the address 0x00 is the broadcast address - it must be used only for commands).
The first byte in the slave-to-master direction contains the address of the unit, shifted to the left by
4 (e.g. the unit with the address 0x05 will return address 0x50).
The second byte in the master-to-slave direction is a command or a data request.
The third, forth and fifth bytes in the master-to-slave direction carry the value of parameter or an
expansion of the command. The third byte is the most significant (MS) byte, the fourth is the less
significant (LS) byte, and the fifth byte is the value after the decimal point.
The second to the sixth bytes in the slave-to-master direction carry data or status from the slave
unit.
The seventh byte in both the master-to-slave and the slave-to-master directions carry the check-
sum, calculated as algebraic sum of bytes 1-6.
All not used bytes are always set to 0xAA.
The format for gain, level, current consumption and temperature is a 2-bytes hexadecimal value in
0.1 dB, 0.1 dBm, 0.1 Amp or 0.1 degree (signed integer).
The format for LNX current is a 2-bytes hexadecimal value in 1 mA step (unsigned integer).
The format for frequency is a 2-bytes hexadecimal value in 1MHz steps (unsigned integer).