Siemens Milltronics BW500/L - Page 141

Communications
11.5 Modbus RTU/ASCII Protocol
BW500 and BW500/L
Operating Instructions, 12/2016, A5E33482052-AD
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Device Identifier (R40,064)
This value identifies the Siemens Milltronics device type and is “2” for the BW500 and BW500/L.
Handshaking Area (Parameter Access)
Built into BW500 and BW500/L is an advanced handshaking area that can be used to read and
write 32 bit parameters.
Mapping
Parameter Read and Write (40,090 – 40,095) is a series of six registers that are used for reading
and writing parameter values to and from the BW500 and BW500/L. The first three registers are
always unsigned integers representing parameters and index values. The second three registers
are the format and value(s) of the parameter.
All parameters normally accessed through the hand-held programmer are available through
these registers:
Address
Description
40,090
Parameter (integer)
40,091
Primary Index (integer)
40,092
Secondary Index (integer)
40,093
Format word (bit mapped)
40,094 Read value, word 1
40,095
Read value, word 2
40,096
Write value, word 1
40,097
Write value, word 2
Reading Parameters
To read parameters through Modbus follow these steps:
1. Send the parameter, its primary index, and its secondary index (usually 0) and format to
registers 40,090, to 40,093.
2. Wait until you can read the above values from the registers (40,090 to 40,093).
3. Read the value from registers 40,094 and 40,095.
Writing Parameters
To set parameters through Modbus follow these steps:
1. Send the parameter, its primary index, and its secondary index (usually 0) to registers
40,090, 40,091, and 40,092.
2. Write the value to registers 40,096 and 40,097
3. Write the desired format word to register 40,093 to enable the BW500 and BW500/L to
interpret the value correctly.