Operating and application notes for SFP modules with the CU1521-0020

Fig.8: CU1521-0020, rotary switch positions and ports

Functionality

The CU1521-0020 communicates via SFP

• with 100BaseX if an SFP type "100 Mbit" is plugged in
• with SGMII 1 Gbit if an SFP type "1 Gbit" is plugged in

Note on FW01: only use in pairs CU1521-0020 <-> CU1521-0020 possible, with identical 1 Gbit SFP on both sides

Explanation:

• 100BaseX: Fast Ethernet standard with a fixed data transfer rate of 100 Mbit
• SGMII (short for Serial Gigabit Media Independent Interface): Interface for Gbit Ethernet, can also transmit net data rates of 100 Mbit and 10 Mbit Ethernet using 10 or 100-fold symbol repetitions.

EtherCAT mode

• All 3 ports X1, X2, X3 are in operation in the order indicated by the rotary switch
• The CU1521-0020 can be used as a 2-port media converter or as a 3-port junction with media converter function
• 100 Mbit EtherCAT is supported (as of 2025), EtherCAT G in preparation
• The ports X1/X2 can be equipped with different SFP, at least one is required.
• The type of SFP used must be selected to match the remote station:
• 100 Mbit SFP with a 100BaseX remote station
• 1 Gbit SFP with one SGMII remote station
• Only 100 Mbit remote stations can be connected to port X3 (RJ45).
• Only SFP modules qualified by Beckhoff should be used to ensure EtherCAT compatibility. The following types have been qualified by Beckhoff (status 2025-05):
• Single-mode 100 Mbit
  Optomedia PT1-S1-4203L
• Multi-mode 100 Mbit
  Optomedia PT1-M4-4023L
• Bidirectional 1 Gbit
  Cisco GLC-BX40-D-I and GLC-BX40-U-I, Bidirectional optical fiber, LC/PC, 40km, 1550/1310nm
  FS 36888 1000BASE-BX-D BiDi SFP 1550nm-TX/1310nm-RX 40km LC/PC (2024)
  FS 36889 1000BASE-BX-U BiDi SFP 1310nm-TX/1550nm-RX 40km LC (2024)

Ethernet mode

• Only the 2 ports X1 and X3 are in operation - the device works as a 2-port media converter
• Different Ethernet data transfer rates (10 Mbit, 100 Mbit, 1 Gbit) can be applied to ports X1 and X3.
• The device operates according to the store-and-forward principle
• Port X1 must be equipped with a suitable SFP
• The device supports "Link Loss Forwarding" and reports the link loss in the direction indicated by the arrow.
• The data transfer rates of ports X1 and X3 depend on the switch position and the data transfer rates of the SFP used and the connected remote stations.
• The data transfer rate of the port to which the arrow is pointing is reduced to the speed of the other port in the CU1521-0020.
• The actual data transfer rates at ports X1 and X3 of a specific combination of SFP and X1/3 remote station can be read from the tables for switch positions 1 and 6.

Fig.22: CU1521-0020 topologies according to switch position in Ethernet mode

Ethernet data transfer rates CU1521-0020 in switch position 6 (X1->X3)

The following tables show the possible transmission types according to the illustration. In switch position 6, the data transfer rate of the X1 remote station determines the data transfer rate of port X3.

Ethernet data transfer rates CU1521-0020 in switch position 1 (X3->X1).

In switch position 1, the data transfer rate of the X3 remote station determines the data transfer rate of port X1.

*) For remote stations on X1 with 1 Gbit or 10 Mbit Ethernet, a 1 G SFP must be used (SGMII).

**) If the remote station on SFP port X1 is slower, its speed is taken over by the SFP in X1.

Application notes for the SFP modules The SFP is not sold by Beckhoff as accessories and is not part of the scope of supply. The SFP tested by Beckhoff should preferably be used. Beckhoff cannot provide a functional guarantee and compatibility with all SFPs available worldwide. When procuring the SFP individually, the following points must be observed: - no SFP+ modules (SFP+ means >1 Gbit) - matching light wavelength - the current consumption of the SFP must not exceed the performance of the carrier device, see technical data there - the SFP must have a maximum permissible operating temperature of at least 85°C In EtherCAT mode, the SFP used must not impair operation (link control, timing).