User's Manual

7ML19985FH04 SITRANS LR 400 – INSTRUCTION MANUAL Page 100
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Appendix VI
The 3 function blocks (Level, Volume, Mass) return 5 bytes of data each:
The first 4 bytes are the floating point representation (IEEE) of the variable. The variables
are the outputs of the function block. The default setting for the variable level is meters.
The default setting for the variable volume is m
3
. The default setting for the variable mass
is kg. You can change the settings of the variables by changing the settings of the
function block. This is typically done using PDM.
The 5th byte is the status word and the list of possible values is given in the chart on
page 101.
The 5 bytes must be read consistently, in a contiguous chunk: they cannot be read byte by
byte, and cannot suffer an interrupt. If you are using an S7-300/400, you will need to use
SFC14 DPRD_DAT: Read Consistent Data of a Standard PD Slave.
If you select a Free Place module to fill one of the slots, this will affect the byte number.
Example 1:
Example 2:
Floating Point Status
Volume
Level byte 1 byte 2 byte 3 byte 4 byte 5
byte 6 byte 7 byte 8 byte 9 byte10byte10
Mass byte 11 byte 12 byte 13 byte 14 byte 15
Floating Point Status
Volume
Free
Place
— — — — —
byte 1 byte 2 byte 3 byte 4 byte 5
Mass byte 6 byte 7 byte 8 byte 9 byte 10
Floating Point Status
Level
Free
Place
byte1 byte 3 byte 4 byte 5
— — — — —
byte 2
Mass byte 6 byte 7 byte 8 byte 9 byte 10