Maximum Delay For Disconnections In Token-Ring Mode - Omron SYSMAC CS1W-CLK13 Operation Manual

Communications Cycle Time
9-2-3

Maximum Delay for Disconnections in Token-ring Mode

Maximum Cycle Time
Delay for Networks
Connected in Order of
Node Addresses
Calculation Example
In this example, A to F in the equation have the following values.
B: 4
C: 8
D: 2
E: 4,024
7 × 8
F:
The communications cycle time in token-ring mode is thus as follows:
1,740 × 4 + 450 × 8 + 1,100 × 2 + 4 × 4,024 + 2 × 7 × 8 + 3,000 = 31,968 ( µ s)
≅ 32 (ms)
And the communications cycle time in token-bus mode is thus as follows:
1,300 × 4 + 110 × 8 + 320 × 2 + 4 × 4,024 + 2 × 7 × 8 + 1,800 = 24,728 ( µ s)
≅ 25 (ms)
Although the redundant transmission paths in token-ring mode ensure that
communications will continue even if there is one disconnection, the commu-
nications cycle time will be affected. The data that is received first from the
two reception interfaces (SL1 and SL2) will be used. A disconnection, how-
ever, may cause the data that should arrive first to be lost, causing a delay
before the data is received on the other interface. The delay will thus be the
time difference between receiving the same data on the two reception inter-
faces (assuming it was received). This delay will occur at each node as the
right to send is passed, and the maximum delay in the overall cycle time will
be the sum of the delay at each node.
On a Controller Link Network, the right to send is passed at the following
times.
• When the token is passed.
• When the nodes being checked from the polling node for network partici-
pation change (depends on the number polled nodes per cycle set in the
network parameters)
• When different nodes send messages requiring responses
The delay in the cycle time will depend on where the disconnection occurs,
but the time to pass the right to send can be reduced by connecting nodes in
order of node address.
The maximum delay in the communications cycle time can be calculated as
follows when the nodes are connected in order of node address.
(A × 4 + B × 2 + 1) × (3 × C + D) ( µ s)
Where,
A: Number of polled nodes per cycle
(value specified in the network parameter)
B: Number of nodes that send messages during the cycle
C: Number of nodes participating in the network
D: Optical Fiber Cable transmission delay time
H-PCF cable:
GI cable:
Communications conditions in this example are as follows:
Transmission distance (with H-PCF cable):
Transmission speed:
Network parameters:
Max node address:
Polled nodes per comm cycle:
Event-frames per comm cycle:
F = 7 × L µ s (L is the cable length in km.)
F = 5 × L µ s (L is the cable length in km.)
8 km
2 Mbps
Defaults
62
4
35
Section 9-2
223