42 Issue
Number:
3
9.5 Endian
Format
Unidrive: #20.13
0 = big endian
1 = little endian
The Unidrive uses word (16-bit) format, but the master controller must
split each word into 2 bytes (high byte and low byte) for transmission
over the Profibus. The "endian format" defines whether the high byte or
low byte is transmitted first. Provided that the master controller and
slave device are using the same endian format, the data word value will
be reconstructed correctly.
The Unidrive Profibus-DP interface uses big endian format by default,
where the high byte is transmitted first, followed by the low byte.
However, some master controllers use little endian format. This results
in "byte swapping" when the data value is reconstructed at the other
end of the network. For example, a value of 0x0102 (258 decimal) may
be reconstructed as 0x0201 or 513 decimal.
If #20.13 is set to 1, the Unidrive Profibus-DP interface will treat all data
received as “little endian”, and use the first byte received as the low
byte of the data word.
NOTE
With firmware V2.05.00 and earlier, the bytes for the non-cyclic data
word are NOT swapped. To use non-cyclic data in “little endian” data
mode, the bytes for each non-cyclic telegram must be swapped
BEFORE they are transferred to the Profibus.
9.6 EVENT
Task
Trigger
on
UD70
The EVENT task is a high priority task in the UD70 that can be triggered
either by the timer/counter unit, or by the Profibus-DP network.
When the fieldbus network is selected as the trigger source, the EVENT
task is triggered in every Profibus-DP network cycle.
#17.23 EVENT
Task
Trigger Source
Comments
0
Timer/Counter
Refer to UD70 Manual for more information.
1
Profibus-DP
The EVENT task is triggered every time
new data arrives from the Profibus-DP
network, and is passed to the UD70.
Care must be taken not to put too much code in the EVENT task. It has
a higher priority than all other UD70 tasks except the INITIAL task, so
an extended EVENT task could easily prevent the SPEED task from
running, and cause the UD70 to trip on “tr54”.
NOTE
This feature is only available with system file V2.07.06 or later.
