Appendix A: Rs-485 Serial Communication Protocol; Introduction; Frame Structure - Advantech SSPBMg–C200–BRE Installation And Operating Manual

11. APPENDIX A: RS-485 SERIAL COMMUNICATION PROTOCOL

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1.1 INTRODUCTION

T his Section describes the RS485 serial interface for interconnection between External Network
M anagement System (NMS) and Advantech Wireless units.
T his protocol supports 2 and 4 wires RS485 interface 9600.N.8.1.
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1.2 FRAME STRUCTURE

Eac h frame starts from start byte 0x55. After this start byte, each frame consists of
Firs t byte:
Mas ter (NMS) to Slave (Advantech Wireless unit): Address of correspo
Wireless unit (0x01 to 0x0F).
Slave to Master: When Advantech Wireless
unit address by 4. For example, unit with address 0x05 will put 0x50 in the address byte.
Second byte:
M aster to Slave: Command byte. The command codes are described in TABLE
S lave to Master: First data or status byte
T hird, forth, fifth and sixth bytes:
M aster to Slave: Value of parameter or expansion of command (third byte if applicable)
S lave to Master: Remaining data or status bytes
S eventh byte:
C heck sum, calculated as algebraic sum of bytes 1 to 6.
A ll not used bytes always - 0xAA.
F ormat for gain, attenuation, level and temperature is a 2-bytes hexadecimal value in 0.1 dB,
0 .1dBm, 0.1 degree (signed integer).
unit sends the respond frame to NMS, it left shifts its
SSPBMg-C200-BRE
7 bytes.
ndent Advantech
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