Technical description
3 Supporting functions
3.7 System clock and
synchronization
VM50.EN004
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129
Parameter Value
Unit Description
Note
SySrc
Internal
DI
SNTP
SpaBus
ModBus
ProfibusDP
IEC-103
IEC101
DNP3
Clock synchronisation source
No sync recognized since
200s
Digital input
Protocol sync
Protocol sync
Protocol sync
Protocol sync
Protocol sync
Protocol sync
Protocol sync
MsgCnt
0 ... 65535,
0 ... etc.
The number of received
synchronisation messages or
pulses
Dev
32767
ms
Latest time deviation
between the system clock
and the received
synchronization
SyOS
10000.000
s
Synchronisation correction
for any constant error in the
synchronizing source.
Set
AAIntv
10000
s
Adapted auto adjust interval
for 1 ms correction
Set
**)
AvDrft Lead
Lag
Adapted average clock drift
sign
Set
**)
FilDev
125
ms
Filtered synchronisation
deviation
Set = An editable parameter (password needed).
*) Astronomically a range –11 ... +12 h would be enough, but for political
and geographical reasons a larger range is needed.
**) If external synchronization is used this parameter will be set
automatically.
***) Set the DI delay to its minimum and the polarity such that the leading
edge is the synchronizing edge.
Synchronisation with DI
Clock can be synchronized by reading minute pulses from
digital inputs, virtual inputs or virtual outputs. Sync source is
selected with SyncDI setting. When rising edge is detected from
the selected input, system clock is adjusted to the nearest
minute. Length of digital input pulse should be at least 50 ms.
Delay of the selected digital input should be set to zero.
Synchronisation correction
If the sync source has a known offset delay, it can be
compensated with SyOS setting. This is useful for
compensating hardware delays or transfer delays of
communication protocols. A positive value will compensate a
lagging external sync and communication delays. A negative