8-3
Section
Data Link I/O Response Time
120
Maximum Communications Cycle Time Delay with Node Addresses Set in Order
The maximum delay in the communications cycle time can be calculated as fol-
lows if the node addresses are set in the order that the nodes are connected in
the network.
A: Number of polled nodes per communications cycle
(value specified in the network parameter)
B: Number of nodes that send messages during the communications cycle
C: Number of nodes connected to network
D: Extra communications time for long-distance cable connections.
If L is the cable length in km, then F = 7
×
L
µ
s for H-PCF cable and
F = 5
×
L
µ
s for GI cable.
(A
×
4 + B
×
2 + 1)
×
(3
×
C + D) (
µ
s)
Communications conditions are as follows:
Type:
Optical Ring
Transmission medium:
H-PCF cable
Transmission distance:
8 km
Baud rate:
2 Mbps (fixed)
Network parameters:
Defaults
Max node address:
62
Polled nodes per comm cycle: 4
Event-frames per comm cycle: 35
Network configuration:
8 nodes
Nodes that send messages:
2 nodes
Bytes in all messages sent:
2,012
2 bytes
In this example, B to F in the equation have the following values.
A:
4
B:
8
C:
2
D:
7
8
The communications cycle time delay for Token Ring Mode is thus as follows:
(4
×
4 +2
×
2 + 1)
×
(3
×
8 + 7
8) = 1,680 (
µ
s)
≅
1.7 (ms)
The percentage change for active data links would be as follows (refer to Cal-
culation Example for Optical Ring Networks with H-PCF Cable under 8-2-1 Ac-
tive Data Links):
(111 + 1.7)/111
×
100
≅
101.5 (%)
The percentage change for inactive data links would be as follows (refer to Cal-
culation Example for Optical Ring Networks with H-PCF Cable under 8-2-2 Inac-
tive Data Links):
(32 + 1.7)/32
×
100
≅
105.3 (%)
8-3
Data Link I/O Response Time
The data links of the Controller Link Support Board require a slight time delay
from the time the data link area of one node is changed until this change is re-
flected in the data link area at another node. This time delay is called the data link
I/O response time.
Calculation Example for
Optical Ring Networks
with H-PCF Cable
