Issue link: https://www.e-digitaleditions.com/i/1472963
July/August/September 2022 I 21 TABLE 1: Recent research by the Single Pair Ethernet System Alliance shows that SPE cabling is theoretically backward compatible with legacy bus cabling systems. FASTER SPEEDS One of the main reasons for Ethernet to be widespread within OT networks is to enable better, stronger, and faster networks. Single-pair Ethernet is designed to bring devices into the Ethernet ecosystem that do not need the higher data rates of high-speed networking (HSN). Rather, SPE focuses on areas that can benefit from switching over to the internet protocol (IP), such as OT network topologies that require very long cable runs or multidrop. Traditional four-pair Ethernet supports up to 10 Gb/s speeds at 100 m (≈328 ft), while SPE supports 10 Mb/s up to 1,000 m (≈3281 ft). There will be a tradeoff between achievable distance and the supplied power. In addition, multipoint communication will be possible for 10 Mb/s at distances up to 25 m (≈82 ft). While SPE seems slow in comparison to four-pair Ethernet, it offers the ability to operate as Ethernet in the same topologies used for legacy protocols at higher speeds, making it an ideal upgrade solution. Recent testing conducted by members of the Single Pair Ethernet Systems Alliance demonstrates that SPE cabling is backward compatible with legacy bus systems cabling, including RS485, Profibus PA, CANbus, and BACnet and can be used as a migration strategy for brownfield installations. This means that 10 Mb/s SPE could become the logical progression from lower speed standards by increasing data transfer over much longer distances up to 1 km (≈3281 ft) and less cabling (two wires). Likewise, 1 Gb/s SPE has the potential to upgrade 100Base-TX PROFINET by delivering much higher transmission speeds, going from 100 Mb/s to 1 Gb/s over half the amount of cable. Although this is an automotive physical layer (PHY), more test data will be required before applying it to industrial or building automation. Table 1 shows that SPE cabling is theoretically backward compatible with legacy bus cabling systems. RS485 Field. Found H1 (Type A, B, C) Profibus DP Profibus PA CANbus BACnet Impedance Ω 115 100 150 100 120 115 Capacitance < 60 nF < 80 nF < 30 nF < 80 nF Typ 40 nF < 100 nF Ohmic Resistance (Ω/km) < 98 < 24 (A), 56 (B), 132 (C) < 55 < 24 (A), 56 (B), 132 (C) < 70 (40m) 26 (1km) Attenuation db/km Not required 3 (Type A), 5 (Type B), 8 (Type C) Not required 3 (Type A), 5 (Type B), 8 (Type C) Not required Not required Frequency Range 31kHz-3MHz 31.25-39kHz 3-20MHz 31.25-39kHz 2 MHz Design 1p SF/UTP 1p SF/UTP 1p SF/UTP 1p SF/UTP 1p SF/UTP 2 wires + GND Conductor > 0.22mm 2 (AWG24) > 0.8mm 2 (A), 0.32 (B), 0.13 (C) > 0.34mm 2 (AWG22) > 0.8mm 2 > 0.25mm 2 to 0.75mm 2 AWG22 (300m) to AWG16 (1200m) Backward Compatible YES Yes but possibly some length restriction NO Yes but possibly some length restriction Yes but possibly some length restriction YES SPE cable is fully compatible SPE cable is compatible, but some restrictions appear SPE cable is NOT compatible