Timing; 350 Supported Functions - GE 350 Communications Manual

MODBUS PROTOCOL

Timing

350 supported functions

2–4
10. is i = N? No: go to 3. Yes: go to 11.
11. A —> CRC
Data packet synchronization is maintained by timing constraints. The receiving device
must measure the time between the reception of characters. If 3.5 character times elapse
without a new character or completion of the packet, then the communication link must
be reset (i.e. all slaves start listening for a new transmission from the master). Thus at 9600
baud a delay of greater than 3.5 x 1 / 9600 x 10 = 3.65ms will cause the communication
link to be reset.
The following functions are supported by the 350 :
• FUNCTION CODE 03H - Read Setpoints
• FUNCTION CODE 04H - Read Actual Values
• FUNCTION CODE 05H - Execute Operation
• FUNCTION CODE 06H - Store Single Setpoint
• FUNCTION CODE 07H - Read Device Status
• FUNCTION CODE 08H - Loopback Test
• FUNCTION CODE 10H - Store Multiple Setpoints
Refer to section 6 of this guide for more details on MODBUS function codes.
CHAPTER 2: RS485 INTERFACE
350 FEEDER PROTECTION SYSTEM – COMMUNICATIONS GUIDE