B.2.2 Physical Layer - GE Multilin W650 Instruction Manual

APPENDIX B B.2 MODBUS W650

B.2.2 PHYSICAL LAYER

ModBus/RTU protocol is independent from the hardware. This way, the physical layer may be in different hardware
configurations: RS232, RS485, fiber optic or Ethernet.
W650 units incorporate a front RS232 port, two rear RS485 or fiber optic ports, and a 10/100Base T port, and in some
configurations two 100BaseFX ports. The data flow in any of the configurations is "half-duplex".
B
Each data byte is transmitted in an asynchronous way and it is formed by: 1 start bit, 8 data bits, 1 stop bit and 1 parity bit if
programmed. Thus you have a 10 or 11-bit data, depending on whether it has parity or not.
The port baud rate and the parity are independent and programmable for each communication port. Any port may be
programmed to baud rates of: 1200, 2400, 4800, 9600, 19200, 38400, 57600 or 115200. Parity may be pair, impair or
without parity.
The master must know the client address with which it is going to communicate. No unit will operate after a master request
if the message address is not its own, except it the address is 0, which is the broadcast address. In this case the relay will
operate, but won't send any reply.
GEK-113032A W650 Wind Generator Protection System B-3