MG.10.O1.02 VLT is a registered Danfoss trademark
30
VLT
®
5000 INTERBUS
■
■
■
■
■
VLT response time
The update time via the INTERBUS 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
(VLT 5000 with INTERBUS option), and 2) the
internal update time, which is the time it takes to
transmit data between the VLT 5000 control card
and the INTERBUS option card.
Communication time (t
com
) depends on the type of
master in use, the total number of bytes transmitet to
all slaves and the total length of the INTERBUS Cable.
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
2
msec
Status word/Actual speed
2
msec
Parameter read via PCD-part
2
msec
Parameter write via PCD1-2
83 msec
Parameter write via PCD3-4
165 msec
Parameter write via PCD5-7
325 msec
Parameter read via PCP
XXY msec
Parameter write via PCP
YYX msec
Timing
■
■
■
■
■
System update time
The system update time is the time it takes to
update all the slaves in the network when using
cyclical communication.
Actual master station delay:
-
The information must be supplied by the
manufacturer of the actual INTERBUS master.
Example:
-
INTERBUS G4 master using 4 words of
Process Data and 1 Word of PCP Data to 12
Slaves on the INTERBUS. The total length of
the INTERBUS Cable is 250m.
Following Formula can be used for calculation the
Cycle-time:
t
z
= [15*(8+n) + 3*m] * t
Bit
+ t
SW
+ 2*t
PH
where
n
the register size
m
the total number of stations
t
Bit
the Bit time = 2µ at 500 kBit/sec
t
SW
software time 0,34 ms for G3 Master
0,70 ms for G4 Master
t
PH
the delay of the medium,
for Cu = 0,016ms*l/Km; Lenght in Km
t
z
= [15*(8+n) + 3*m] * t
Bit
+ t
SW
+ 2*t
PH
t
z
= [15*104 + 3*13] *2*10
-6
+ 0,7+
0,016 * 0,250
t
z
= 3.902 ms
VLT®5000
Control
Card
Interbus
option
Master
t
com
t
int
