Controller Link Units Operation Manual

271
Message Delay Times Section 8-4
Example
In this example, the maximum transmission delay is calculated for an instruc-
tion sending 256 words of data in a system with 32 nodes. Network specifics
are detailed below:
Baud rate: 2 Mbps
Max. node number: 32
Number of nodes: 32
Number of polled nodes: 4
Number of words: 256
Data link: halted
Note This communications cycle time is calculated assuming that there is no node
that transmits event frames before the SEND command is issued.
RECV(98) Instruction
Maximum Delay Time
The following indicates the data flow which will yield the maximum transfer
interval from the time the RECV(98) instruction is executed by the user pro-
gram to the time the Controller Link Unit stores the data in the local Unit’s
memory area.
Note Be sure to take into account the time required for data links and program exe-
cution, which are not included in the following example.
Max. transmission delay = Link Unit servicing interval (source node) + Trans-
mission processing (command) + Communications cycle + Transmission
delay (command) + Reception processing (command) + Link Unit servicing
Link Unit servicing (source node) PLC cycle time (source node)
Transmission processing 0.00125 × 256 + 3 = 3.32 ≅ 3.3 ms
Communications cycle time (See note.) 600 × 4 + 110 × 32 + 320 × 0 + 4 ×
0 + 2,290 = 8,210 µs ≅ 8.2 ms
Transmission delay (command) 0.008 × 256 + 0.112 = 2.16 ≅
2.2 ms
Reception processing 0.00125 × 256 + 2.3 = 2.62 ≅
2.6 ms
Link servicing interval (destination node) PLC cycle time (destination node)
Total (max. transmission delay) PLC cycle time (source node) ×
2 + PLC cycle time (destination
node) + Peripheral servicing
time (destination node) +
16.3 ms
RECV(98) executed
Link Unit servicing
(source node)
Transmission processing
(command)
Communications cycle
Data stored
Link Unit servicing (destination
node)
Max. transmission delay
Transmission processing
(response)
Reception processing
(response)
Transmission delay
Reception processing
(command)
Transmission delay