3-40 C60 Breaker Protection System GE Multilin3.3 DIRECT INPUT/OUTPUT COMMUNICATIONS 3 HARDWARE3d) 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 DPLL (digital phase lock loop) 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 SCC (serial communication controller) receive clock.3.3.6 RS422 AND FIBER INTERFACEThe following figure shows the combined RS422 plus fiberoptic interface configuration at 64K 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.When using a LASER Interface, attenuators can be necessary to ensure that you do not exceedmaximum optical input power to the receiver.Figure 3–45: RS422 AND FIBER INTERFACE CONNECTIONConnections shown above are for multiplexers configured as DCE (data communications equipment) units.3.3.7 G.703 AND FIBER INTERFACEThe figure below shows the combined G.703 plus fiberoptic interface configuration at 64 kbps. The 7E, 7F, 7G, 7Q, and 75modules are used in configurations where channel 1 is employed via the G.703 interface (possibly with a multiplexer) andchannel 2 via direct fiber. AWG 24 twisted shielded pair is recommended for external G.703 connections connecting theshield to pin 1a at one end only. For the direct fiber channel, address power budget issues properly. See previous sectionsfor additional details on the G.703 and fiber interfaces.When using a laser Interface, attenuators can be necessary to ensure that you do not exceed themaximum optical input power to the receiver.Figure 3–46: G.703 AND FIBER INTERFACE CONNECTIONNOTICETx2 Rx2842777A3.CDR~8a7L, 7M, 7N,7P, and 74ShieldTx –Rx –Tx +Rx +RS422communications~4b~3a~3b~6a~2aRS422channel 1Surge+–~1a~1bClockchannel 1Common ~2bCOMFiberchannel 2NOTICERx2Tx2842778A2.CDR~3b75, 7E, 7F, 7G,and 7QRx +ShieldTx –Rx –Tx +G.703communications ~2b~1b~1a~3a~2aG.703channel 1SurgeFiberchannel 2
