FCM 300 PROFIBUS / VLT 2800 PROFIBUS
MG.90.A2.02 – VLT is a registered Danfoss trademark
21
DP
FREEZE/UNFREEZE
FREEZE/UNFREEZE can be used to get simultaneous
reading of Process Data for example output current
from several slaves. A FREEZE command will freeze
the current actual values and on request the slave will
send back the value that was present when the
FREEZE command was received. The actual values
will be updated when a new FREEZE or UNFREEZE
command is received.
See the example below where the left column holds
the current values read by the master and the three
right columns hold the actual output current of the
three slaves.
Actual slave output current
VLT
VLT
VLT
DP master reads address:
Address 3
Address 4
Address 5
1. Address 3 output current = 2 A
⇐
2 A
3 A
4 A
2. Address 4 output current = 5 A
2 A
⇐
5 A
2 A
3. Address 5 output current = 3 A
3 A
2 A
⇐
3 A
4. FREEZE command to all addresses
⇒
1 A
⇒
3 A
⇒
3 A
5. Address 3 output current = 1 A
⇐
4 A
2 A
5 A
6. Address 4 output current = 3 A
2 A
⇐
2 A
2 A
7. Address 5 output current = 3 A
3 A
1 A
⇐
2 A
8. UNFREEZE command to all adresses
⇒
2 A
⇒
3 A
⇒
4 A
Reading as by 1, 2 and 3