Specifications

Table 5: Local FC Bus Rules
Rules/LimitsCategory
NAE55 Series models can support up to two local FC buses.
Note: When a second FC bus is added to the NAE, be sure the trunk number has not been
used on the NAE and enter a Network Address that is unique for the entire site. This
applies for any model of NAE.
NAE45 Series models can support one local FC bus.
NAE35 Series models can support one local FC bus (but an NAE35 FC bus supports only
half the number of devices that are supported on an FC bus on an NAE45 or NAE55).
NCE25 Series models can support one local FC bus. NCEs must be ordered specifically as
N2 or MS/TP models.
Note: An FC port on an NAE/NCE can connect to only one bus segment on an FC bus.
Only a daisy-chain topology is allowed (no T or Star topology configurations).
Note: Refer to the Network Automation Engine (NAE) Product Bulletin (LIT-1201160) and
the Network Controller Engine Product Bulletin (LIT-12011283) for complete
information on MS/TP bus support on NAE and NCE models.
General
NCE25 models support 32 MS/TP devices (maximum) on an FC bus trunk and up to 3 bus
segments.
NAE35 models support half the number of devices that an NAE45 supports.
NAE45 and NAE55 models support the following device limits on an FC bus trunk:
When all of the devices connected on the FC bus are Metasys FACs, FECs, VMA16s, and/or
IOMs, the device and bus segment limits are as follows:
• 100 devices total per FC bus (maximum)
• 3 bus segments per FC bus (maximum)
• 50 devices per bus segment (maximum, not to exceed 100 devices per FC bus)
When one or more non-FX family device is connected on the FC bus, the device and bus
segment limits are as follows:
• 64 devices total per FC bus (maximum)
• 3 bus segments per FC bus (maximum)
• 32 devices per bus segment (maximum, not to exceed 64 devices per FC bus)
Number of Devices and Bus
Segments
Bus segments on an FC bus are connected with repeaters (only). Up to two cascaded
repeaters may be applied to an FC bus (to connect three bus segments).
When all of the devices connected on the FC bus are Metasys FACs, FECs, VMA16s, or
IOMs, the cable length limits (using 22 AWG 3-wire twisted, shielded cable) are as follows:
• Each bus segment can be up to 1,520 m (5,000 ft) in length.
• Each FC bus can be up to 4,750 m (15,000 ft) in length.
When one or more non-FX family device is connected on the FC bus, the device and bus
segment limits are as follows:
•
Each bus segment can be up to 1,220 m (4,000 ft)
1
in length.
•
Each FC bus can be up to 3,660 m (12,000 ft)
1
in length.
Note: Do not place slave devices on the FC Bus. Slave devices on the FC bus are not
supported.
Cable Length for FC Bus and
Bus Segments
When using fiber-optic connections: 2,010 m (6,600 ft)
1
between two fiber modems.
22MS/TP Communications Bus Technical Bulletin