68 Standard programposi features
select the format. If you select a 32-bit format, the subsequent data word is also
automatically reserved.
Example 2: Transmitting a 32-bit integer over fieldbus
Parameters 90.05 Load position scaled and 90.65 Pos counter init value are real-type
numbers.
In this example, 123456.78 is to be used as the initial value sent from the PLC. To
send the number as an integer over the fieldbus, multiply the value by 100 and select
it to be transmitted as two data words:
• 12345678 = BC614Eh
• 614Eh = 24910
• BCh = 188
• FBA data out x = 188
• FBA data out (x + 1) = 24910.
The drive will thus receive a 32-bit integer. To restore the original two decimal places,
set parameter 90.38 Pos counter decimals to 2. This will divide the integer by 100
before it is written into 90.65 Pos counter init value. Parameter 90.05 Load position
scaled will also be scaled, so when read by the PLC, it will still appear as an integer
(12345678).
90.38 Pos counter decimals = 2
90.65 Pos counter init value = 123456.78
Example 3: Transmitting a 32-bit floating point number over fieldbus
In this example, 66770.125 is used as the initial value sent from the PLC. To transmit
a 32-bit floating-point value, split it into two 16-bit words.
According to IEEE 754, the value 66770.125 converts to 47826910h including the
sign, exponent and significand.
High word: 4782h = 18306
Low word: 6910h = 26896
For eg. PROFIBUS, these values can be set as
FBA data out x = 18306
FBA data out (x + 1) = 26896.
For ABB Automation using DDCS communication, the two words can be transmitted
as eg. data words 12.1 and 12.2 respectively.
When configuring the data selection parameters, select the 32-bit floating-point
number format for parameters 90.65 Pos counter init value and 90.05 Load position
scaled.
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