Advantech AMT SSPB-Ci60, Installation And Operating Manual

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SSPB-Ci60
10. APPENDIX A: RS-485 SERIAL COMMUNICATION PROTOCOL
The protocol described in this Section is used for the interconnection between the SSPB 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.
10.1 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 byte in the master-to-slave direction is an expansion of command (if applicable).
The forth, fifth and sixth bytes in the master-to-slave direction carry the value of parameter. The
fourth byte is the most significant (MS) byte, the fifth is the less significant (LS) byte, and the
sixth 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 (N/U) bytes are always set to 0xAA.
The format for gain, power 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 frequency is a 2-bytes hexadecimal value in MHz (unsigned integer). The third
byte contains the frequency after decimal point in 125 kHz steps (0x00=0; 0x01=125kHz;
0x02=250kHz; 0x03=375kHz; 0x04=500kHz; 0x05=625kHz; 0x06=750kHz; 0x07=875kHz).
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