AN3349| Application Note
Maxim/Dallas > App Notes > TELECOM Keywords: Loopback, loopback operation, DS2156, DS26101, DS26102, Utopia, LLB, RLB, FLB, PLB, DLB, local loopback, remote loopback, framer loopback, payload loopback, diagnostic loopback, per-channel loopback
Sep 10, 2004
APPLICATION NOTE 3349
T1/E1 Loopback Operation for Dallas Semiconductor T1/E1/J1 transceivers
Abstract: This application note contains an overview of the loopback functions for Dallas Semiconductor T1/E1/ J1 transceivers. Loopback modes are useful for diagnostic testing of the device or equipment. 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. The signals from both ends can be compared. The discrepancy between the two helps to trace the fault.
Introduction
This application note contains an overview of the loopback functions for Dallas Semiconductor T1/E1/J1 transceivers. T1 and E1 are terms used to refer to the transmission of 1.544 Mbps and 2.048 Mbps over any media. Loopback modes are useful for diagnostic testing of the device or equipment. 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. The signals from both ends can be compared and any discrepancy helps to trace the fault.
Loopback
There are six types of loopback supported by Dallas Semiconductor T1/E1/J1 transceivers. 1. 2. 3. 4. 5. 6. Remote Loopback (RLB) Local Loopback (LLB) Framer Loopback (FLB) Diagnostic Loopback (DLB) Payload Loopback (PLB) Per-Channel Loopback (PCLB)
Remote Loopback (RLB)
This loopback allows the user to test the far end of the equipment link. From the far end equipment, the signal loops through the LIU and the Jitter attenuator. When the RLB bit of the control register is set to low, then Remote loopback is disabled. When the RLB bit of the control register is set to high, the Remote loopback is enabled. In Remote loopback, data input by RTIP and RRING is transmitted back to TTIP and TRING through the jitter attenuator. Data continues to pass through the receive-side framer of the device as it would normally. Data from the transmit-side formatter is ignored.
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