3-34 F35 MULTIPLE FEEDER PROTECTION SYSTEM – INSTRUCTION MANUALDIRECT INPUT AND OUTPUT COMMUNICATIONS CHAPTER 3: INSTALLATION33.4.5.4 Receive timingThe RS422 interface utilizes NRZI-MARK modulation code and therefore does not rely on an Rx clock to recapture data.NRZI-MARK is an edge-type, invertible, self-clocking code.To recover the Rx clock from the data-stream, an integrated digital phase lock loop (DPLL) circuit is utilized. The DPLL isdriven by an internal clock, which is 16-times over-sampled, and uses this clock along with the data-stream to generate adata clock that can be used as the serial communication controller (SCC) receive clock.3.4.6 RS422 and fiber interfaceThe following figure shows the combined RS422 plus fiberoptic interface configuration at 64 K baud. The 7L, 7M, 7N, 7P,and 74 modules are used in two-terminal with a redundant channel or three-terminal configurations where channel 1 isemployed via the RS422 interface (possibly with a multiplexer) and channel 2 via direct fiber.AWG 20-24 twisted shielded pair is recommended for external RS422 connections and ground the shield only at one end.For the direct fiber channel, address power budget issues properly.Figure 3-41: RS422 and fiber interface connectionThe connections shown in the figure are for multiplexers configured as data communications equipment (DCE) units.3.4.7 G.703 and fiber interfaceThe following figure shows the combined G.703 plus fiberoptic interface configuration at 64 kbps. The 7E, 7F, 7G, 7Q, and75 modules are used in configurations where channel 1 is employed via the G.703 interface (possibly with a multiplexer)and channel 2 via direct fiber. AWG 24 twisted shielded pair is recommended for external G.703 connections connectingthe shield to pin 1a at one end only. For the direct fiber channel, address power budget issues properly. See previoussections for details on the G.703 and fiber interfaces.NOTICE When using a laser interface, attenuators can be necessary to ensure that you do not exceedmaximum optical input power to the receiver.NOTICE When using a laser interface, attenuators can be necessary to ensure that you do not exceed themaximum optical input power to the receiver.Tx2 Rx2842777A2.CDR~8a7L, 7M, 7N,7P, and 74ShieldTx –Rx –Tx +Rx +RS422communications~4b~3a~3b~6a~2aRS422channel 1Surge+–~7a~8bClockchannel 1Common ~2bCOMFiberchannel 2
