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Appendix E – ModBus Management Support and Memory Ma
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RS400 271 ROS™ v3.5
Text
Simple ASCII representation of the information related to the product. ASCII characters’ most
significant byte of register comes first.
E.g. Read Multiple Registers request to read Product Identification from location 0x0000
0x04 0x00 0x00 0x00 0x08
Response may look like:
0x04 0x10 0x53 0x59 0x53 0x54 0x45 0x4D 0x20 0x4E 0x41 0x4D 0x4D
0x00 0x00 0x00 0x00 0x00
In the above response starting from byte 3 until the end there’s ASCII representation of the
characters for the product identification, which says “SYSTEM NAME”. Since the length of this
field is smaller than 8 registers, the rest of the field are filled with zeros.
Cmd
This format is used to instruct the device to set the output to either ‘true’ or ‘false’. The most
significant byte comes first.
FF 00 hex requests output to be True.
00 00 hex requests output to be False.
Any value other than the suggested values does not affect the requested operation
E.g. Write Multiple Registers request to clear alarms in the device.
0x10 0x00 0x80 0x00 0x01 2 0xFF 0x00
FF 00 for register 00 80 would clear the system alarms
00 00 would not clear any alarms
Response may look like:
0x10 0x00 0x80 0x00 0x01
Uint16
Standard Modbus 16 bit register
Uint32
Standard 2 Modbus 16 bit registers – First register would hold higher 16 bits of the value and
seconds register would hold lower 16 bits from the 32 bit value
PortCmd
Descriptive bit layout (1= Requested Action is True; 0 bit = Requested Action is false) per port
PortCmd at this time provides a bit layout of max of 32 ports hence utilizing 2 Modbus registers
First Modbus register corresponds to ports 1 – 16
Second Modbus register corresponds to ports 17 – 32 for a particular action
Bits that do not apply to a particular product are always set to zero. See example for details.
Bit Value 1 – Requested action is true (e.g. This particular port is “Up”)
Bit Value 0 – Requested action is false (e.g. The particular port is “Down”)