![]() In this loopback mode, the transmitted data is in sync with RCLK instead of TCLK. When payload loopback is enabled, a signal from RTIP/RRING, passes through the LIU and the Framer and loops back to TTIP/TRING. When the PLB bit of the control register is set to high, then payload loopback is enabled. When the PLB bit of the control register is set to low, then payload loopback is disabled. This loopback reframes and reformats the data. Payload loopback is useful to verify that the user is receiving a properly formatted data pattern. Typical diagnostic loopback mode operation. Receive active-edge selection bit should be configured as the opposite edge of that used by the transmit section of the same SCT.įigure 4. Receive physical interface mode should be configured with the same value as transmit physical interface mode. ![]() In diagnostic loopback, data, clock, and frame-pulse indication generated by the transmit section of the SCT are used instead of the corresponding signals from the physical layer device. This is applicable for Maxim telecom parts like DS2156. Diagnostic loopback bypasses the LIU and the framer sections of the device.ĭiagnostic loopback enables the transmit data packet to be looped back onto the receive side of the UTOPIA bus. Diagnostic Loopback (DLB)ĭiagnostic loopback uses the UTOPIA section of the device only. When using framer loopback, RCLK can not be connected to TCLK during this loopback because this causes an inoperative condition.įigure 3. In framer loopback mode, all receive-side signals take on timing synchronous with TCLK instead of RCLKI. In E1 mode, normal data is transmitted at TPOSO and TNEGO. In framer loopback in T1 mode, an unframed all-ones code is transmitted at TPOSO and TNEGO. This loopback checks the functionality of the framer. When framer loopback is enabled, the signal from TSER passes through the framer to RSER. When the FLB bit of the control register is set to high, then framer loopback is enabled. When the FLB bit of the control register is set to low, then framer loopback is disabled. Data is routed from TSER to RSER and the clock is routed from TCLK to RCLK. ![]() In framer loopback (FLB), the Maxim devices loop data from the transmit side back plane to the receive side. This loopback is useful for testing and debugging applications. Data in local loopback passes through the jitter attenuator.įigure 2. Data received at RTIP and RRING is replaced with the data being transmitted. In local loopback, data is transmitted as normal through the transmit side of the transceiver. When the LLB bit of the control register is set to high, then local loopback is enabled. When the LLB bit of the control register is set to low, then local loopback is disabled. Local loopback is also called digital loopback, because the device loop backs the data through the digital circuitry of the device. Local loopback allows the user to route data from TSER to RSER and clock from TCLK and RCLK. Data from the transmit-side formatter is ignored.įigure 1. Data continues to pass through the receive-side framer of the device as it would normally. In remote loopback, data input by RTIP and RRING is transmitted back to TTIP and TRING through the jitter attenuator. When the RLB bit of the control register is set to high, the remote loopback is enabled. When the RLB bit of the control register is set to low, then remote loopback is disabled. From the far end equipment, the signal loops through the LIU and the jitter attenuator. This loopback allows the user to test the far end of the equipment link. There are six types of loopback supported by Maxim T1/E1/J1 transceivers. The signals from both ends can be compared and any discrepancy helps to trace the fault. In loopback mode, the device loops the signal from one end of the device to the other end of the sending device, after it has passed through a network or across a particular link. Loopback modes are useful for diagnostic testing of the device or equipment. T1 and E1 are terms used to refer to the transmission of 1.544Mbps and 2.048Mbps over any media. This application note contains an overview of the loopback functions for Maxim T1/E1/J1 transceivers. The discrepancy between the two helps to trace the fault. The signals from both ends can be compared. In loopback mode, the device loops the signal from one end of the device to the other end of the sending device after it has passed through a network or across a particular link.
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