GE Industrial Solutions MX350 Communications Guide - Manual (Page 10)

6 MX350 AUTOMATIC TRANSFER CONTROL SYSTEM – COMMUNICATIONS GUIDE
RS485 INTERFACE (MODBUS RTU) COMMUNICATIONS GUIDE
Function Code 03H Modbus implementation: Read Holding Registers
MX350 implementation: Read Setpoints
For the MX350 implementation of Modbus, this function code can be used to read any
setpoints (“holding registers”). Holding registers are 16 bit (two byte) values transmitted
high order byte first. Thus all MX350Setpoints are sent as two bytes. The maximum
number of registers that can be read in one transmission is 125.
The slave response to this function code is the slave address, function code, a count of the
number of data bytes to follow, the data itself and the CRC. Each data item is sent as a two
byte number with the high order byte sent first.
For example, consider a request for slave 17 to respond with 3 registers starting at address
006B. For this example the register data in these addresses is as follows:
Command Number Description
196 Reset Time S2 Available Counter
197 Alarm Silence
198 Control to bypass W-timer
199 Control to bypass T-timer
200 Net Ctrl Test on No load
201 Fast Load Test Control
202 Regular Load Test Control
203 Auto/Manual retransfer to S1
204 Auto/Manual transfer to S1/S2
205 Net Ctrl Load Shed for S1
206 Net Ctrl Inhibit Transfer to S2
207 Net Ctrl Inhibit Transfer to S1
208 Net Ctrl Transition Mode Selector
209 Command to Bypass R50
210 Confirm Bypass R50
211 Cancel Bypass R50
212 Bypass Pending Exerciser
213 Cancel Exerciser Bypass
214 Net Ctrl Auto Transfer Inhibit
215 Net Ctrl Auto Transfer Relay
216 Net Ctrl Bypass Active ATS Timer
217 Net Ctrl Exerciser Cancel
218 Net Ctrl Generator Start
219 Net Ctrl Generator Stop
220 Net Ctrl Load Shed for S2
221 Net Ctrl Prime Source Selection
222 Net Ctrl Test Mode Cancel
223 Net Ctrl Test On Load
224 Net Ctrl Transfer Commit
Address Data
006B 022B
006C 0000
006D 0064