Danfoss FCD 300 PROFIBUS, Manual, Page: 15 / 39

FCM 300 PROFIBUS / VLT 2800 PROFIBUS
MG.90.A2.02 – VLT is a registered Danfoss trademark 15
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FC motor / VLT 2800 response time
The update time via the PROFIBUS connection can
be divided in two parts:
1) The communication time, which is the time it takes
to transmit data from the master to the slave (FC
motor / VLT 2800 with PROFIBUS), and 2) the
internal update time, which is the time it takes to
transmit data between the FC motor / VLT 2800
control card and the PROFIBUS.
Timing
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System update time
The system update time is the time it takes to
update all the slaves in the network when using
cyclical communication. The drawing below shows
the value which is obtainable in theory at 2 input
and 2 output bytes.
Communication time (t
com
) depends on the actual
transmission speed (baudrate) and the type of master
in use. The minimum obtainable communication time
with the FC motor / VLT 2800 with PROFIBUS is
approx. 100
µ
sec per slave, when using DP
communication with 4 bytes of data (PPO type 3) at 3
Mbaud. More data or lower transmission speed will
increase the communication time.
The internal update time (t
int
) depends on the type of
data in question as there are different channels for the
data transfer where time critical data e.g. control
word has highest priority. The internal update time for
the different types of data are stated below.
Update
Data time, t
int
Control word/Main reference
(part of PPO) 42 msec
Status word/Actual output frequency
(part of PPO) 40 msec
Parameter read (PCD 1-8) 40 msec
Parameter write (PCD 1-2) 160 msec
Parameter write (PCD 3-4) 320 msec
Parameter write (PCD 5-8) 640 msec
Parameter read (PCV) 41 msec
Parameter write (PCV) 40 msec