BECKHOFF EtherCAT Technology Section I - Manual (Page 74)

Distributed Clocks
I-54 Slave Controller – Technology
And for the other direction:
t
CB
= ((t
B1
– t
B0
) – (t
C1
– t
C0
) – t
Diff
) / 2
Propagation delay between Slave E and F
The propagation delays between slave E and F are calculated like the delays between slave C and D:
t
EF
= t
PE
+ t
WEF
t
FE
= t
PF
+ t
WEF
Assuming that the processing delays of slave E and F are identical (t
P
= t
PE
= t
PF
):
t
EF
= t
FE
= (t
E1
– t
E0
) / 2
Propagation delay between Slave B and E
The propagation delays between slave B and E (t
BE
and t
EB
) are calculated as follows:
t
BE
= t
FB
+ t
WBE
t
EB
= t
FE
+ t
WBE
Assuming that the processing delays of slaves B to F are identical (t
P
= t
Px
), and the difference
between forwarding and processing delay of these slaves is t
Diff
= t
Px
– t
Fx
:
t
BE
= t
EB
= t
P
– t
Diff
+ t
WBE
The Receive Times Port 1 and 2 of slave B have the following relation:
t
B2
= t
B1
+ t
BE
+ t
EF
+ t
FE
+ t
EB
So the propagation delay between slave B and E is
2*t
BE
= (t
B2
– t
B1
) – t
EF
– t
FE
t
BE
= t
EB
= ((t
B2
– t
B1
) – (t
E1
– t
E0
)) / 2
Propagation delay between Slave A and B
The propagation delays between slave A and B are calculated as follows:
t
AB
= t
PA
+ t
WAB
t
BA
= t
FB
+ t
WAB
Assuming that the processing delays of all slaves are identical (t
P
= t
Px
), and the difference between
forwarding and processing delay of these slaves is t
Diff
= t
Px
– t
Fx
:
t
AB
= t
P
+ t
WAB
t
BA
= t
AB
– t
Diff
The Receive Times of slave A have the following relation:
t
A1
= t
A0
+ t
AB
+ (t
B1
– t
B0
) + (t
B2
– t
B1
) + t
BA
So the propagation delay between slave A and B is
t
AB
= ((t
A1
– t
A0
) – (t
B2
– t
B0
) + t
Diff
) / 2
And for the other direction:
t
BA
= ((t
A1
– t
A0
) – (t
B2
– t
B0
) – t
Diff
) / 2