Overview
The line interface unit (LIU) can be completely decoupled from the framer/formatter to interface to optical, HDSL, or other devices with an NRZ interface. It can then be used to corrupt data, insert framing errors, or insert CRC errors, etc.

The framer/formatter can generate/detect either bipolar or NRZ data format (determined by the ODF bit). Table 1 shows the register settings for the output data format. Figures 1 and 2 show how to interface the framer/formatter to devices with bipolar or NRZ data modes.

When the LIU receive side is interfaced to a device with NRZ data format, an OR-gate must be added to convert the bipolar data format into NRZ. See Figures 3 and 4 for both data mode applications.

Table 1. Output data format (ODF) regsiter settings

DS21352/552/Q352/Q552
CCR1: Common Control Register 1 (Address = 37 Hex)