
Maximum Transmission Delays: Writing/Reading to CPU Unit | Section |
For details, refer to the CPU Unit operation manual.
CPU Bus Unit Service Processing Time
The processing time will be as follows, depending on the CPU processing mode settings at the CPU Unit.
CPU execution mode | Processing time considerations | |
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Normal Mode | 4% of CPU Unit cycle time | |
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Priority peripheral ser- | Ethernet Unit is given | Time slice peripheral servicing |
vicing | priority. | execution time |
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| Ethernet Unit is not | Set peripheral servicing time |
| given priority. | (Default: 4% of CPU Unit cycle |
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Parallel processing with | Set peripheral servicing time | |
synchronous memory | (Default: 4% of CPU Unit cycle time) | |
access |
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Parallel processing with | 1 ms max. |
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asynchronous memory |
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access |
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For details, refer to the CPU Unit operation manual.
Transmission Processing Number of words sent ⋅ 0.003 + 0.704 ms
(Response)
Note The actual operating environment can cause transmission delays larger than those calculated with the methods given here. Among the causes of longer delays are the following: traffic on the network, window sizes at network nodes, traffic through the Ethernet Unit (e.g., simultaneous socket servicing and FTP server communications, etc.), and the system configuration.
Example Calculations The following example shows calculations for sending 256 words between two PLC nodes using SEND(090). Calculations are shown in the following table.
Conditions
CPU cycle time: 10 ms
CPU execution mode: Normal
CPU uniform peripheral servicing time: Default (4%)
Baud rate:
Item | Calculation |
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Personal computer transmission pro- | |
cessing time |
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Transmission delay (command) | 256 ⋅ 0.0013 + 0.0118 = 0.3446 ≈ 0.3 ms |
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Reception processing time local | 256 ⋅ 0.003 + 0.704 = 1.472 ≈ 1.5 ms |
node) (command) |
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CPU Bus Unit service cycle (local | 10 ms |
node) |
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CPU Bus Unit service processing | 0.4 ms |
time (local node) |
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Transmission processing time (local | 0.704 ms ≈ 0.7 ms |
node) (response) |
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Transmission delay (command) | 0.0118 ms ≈ 0.1 ms |
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Personal computer reception pro- | |
cessing time |
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Maximum transmission delay time | Personal computer transmission/reception |
| processing time + 0.3 +1.5 + 10 + 0.4 + 0.7 + |
| 0.1 = personal computer transmission/recep- |
| tion processing time + 13.0 ms |