Siemens Milltronics BW500 Operating Instructions Manual page 148

Communications
11.5 Modbus RTU/ASCII Protocol
Parameter Values
Bit Mapped bits are packed into registers in groups of 16 bits (1 word). In this manual we
number the bits from 1 to 16, with bit 1 being the least significant bit and bit 16 referring to the
most significant bit.
16
MSB
Large numbers are put into unsigned 32 bit integers with a fixed decimal place of three. For
example, a value of '7345' represents a value in the BW500 '7.345'. The default word order is
that the first word is the most significant word (MSW) and the second word (register) is the least
significant word (LSW).
For example, if we read R41,431 as a 32-bit, the 32 bits would look like the following:
16
32
The whole is read as a 32-bit integer. The most significant byte (MSB) and least significant byte
(LSB) can be reversed to accommodate some Modbus drivers.
Text Messages
If a Siemens Milltronics device parameter returns a text message, that message is converted to
a number and provided in the register. The numbers are shown in the table below:
Number
22222
30000
30001
30002
30003
30004
30005
30006
30007
30008
30009
30010
30012
30013
30014
-32768
32767
146
15 14 13 12
R41,431
MSB
11 10 9 8
1 16 LSB
32-bit integer value (UNINT32)
Text Message as Displayed on LCD
invalid value
off
on
= = = =
(parameter does not exist)
err
err1
open
shrt
pass
fail
hold
hi
de
en
value is less than -20,000
value is greater than 20,000
Operating Instructions, 12/2016, A5E33482052-AD
7 6 5 4 3
R41,432
BW500 and BW500/L
2 1
LSB
1
1