Siemens Milltronics SF 500 - Modbus Format; Modbus Register Map

Page 78 Milltronics SF 500 - INSTRUCTION MANUAL 7ML19985CN01
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Communications
Modbus Format
To give you a better idea of how a Modbus message works, a master on network would
send a message in a format similar to this:
Where:
Station address the network address of the slave being accessed
Function Code number that represent a Modbus command, either:
03 read function
06, 16 write functions
Information depends on function code
Error Check Cyclical Redundancy Check (CRC) for RTU and Longitudinal
Redundancy Check (LRC) for ASCII
There is more to the frame than is described above, this is shown to give the user a
general idea of what is going on. For a full description, refer to the Modbus
specifications.
Modbus Register Map
The memory map of the SF 500 occupies the Modbus holding registers (R40,001 and up).
The SF 500 makes it easy for users to get useful information via Modbus. The following
chart gives an overview of the different sections.
Register Map for SF 500:
Note: When using a commercial Modbus driver all of the message details are
handled for you.
Station
address
Function
code
Information
Error
check
Map Legend Description
Type Arbitrary classification of registers.
Description Brief description or title of associated register.
Start
Provides the starting address for the register(s) where the parameter
values are to be read from or written to.
Number R
The number of registers required to read or write the complete
parameter value. Where the number of registers (6) are addressed in
incrementing sequence from the start register.
Parameter Values Refer to
Parameter Values , page 87.
Read Identifies the read / write capability for the register being addressed.
Reference Provides reference documentation for the register being addressed.