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4.2 Calculating Communications Cycle Times
4.2.1 Communications Cycle Time
The communications cycle time is the time from when an I/O command is sent to a
DeviceNet Slave on the network until the next I/O command transmission is made.
The communications cycle time must be set when the 260IF Module is used as a DeviceNet
Master. This setting is not required when the 260IF Module is used as a Slave.
4.2.2 Calculating Communications Cycle Times
The communications cycle time can be found from the total of the communications times
required for each Slave device.
Communications cycle time [ms] =Σ (Communications time with Slave)
The calculations for communications time with Slaves may differ from the actual communi-
cations times depending on the length of the network and the number of connections with
other devices.
Communications Times with Slaves
The communications times with Slaves may be grouped in the following eight categories
based on the number of communications bytes of the Slave. The following abbreviations are
used:
No: Number of output data bytes
Ni: Number of input data bytes
TRUND (N/7): Quotient of No or Ni divided by 7. Decimal places are truncated.
MOD (N/7): Remainder when No or Ni is divided by 7.
Tb: 2 for a baud rate of 500 kbps, 4 for 250 kbps, 8 for 125 kbps.
1. Slaves with 8 bytes or less of output data
2. Slaves with 8 bytes or less of input data
www.dadehpardazan.ir 88594014-15
Master
Slaves
Fig 4.2 Master Communications Cycle Time
(94+8 × No) × Tb + 600[µs]
(94+8 × Ni) × Tb + 600[µs]
4-7
4.2 Calculating Communications Cycle Times
Communications cycle time
4
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