LEN0, LEN1, LEN2 - Line Length Selection, Pins 23, 24 and 25. (Hardware and Extended

Hardware Modes)

Determines the shape and amplitude of the transmitted pulse to accommodate several cable types

and lengths. See Table 3 for information on line length selection. Also controls the receiver

slicing level and the line code in Extended Hardware Mode.

LLOOP - Local Loopback, Pin 27. (Hardware and Extended Hardware Modes)

Setting LLOOP to a logic 1 routes the transmit clock and data through the jitter attenuator to the

receive clock and data pins. TCLK and TPOS/TNEG (or TDATA) are still transmitted unless

overridden by a TAOS request. Inputs on RTIP and RRING are ignored.

MODE - Mode Select, Pin 5.

Driving the MODE pin high puts the line interface in the Host Mode. In the host mode, a serial

control port is used to control the line interface and determine its status. Grounding the MODE

pin puts the line interface in the Hardware Mode, where configuration and status are controlled

by discrete pins. Floating the MODE pin or driving it to +2.5 Vselects the Extended Hardware

Mode, where configuration and status are controlled by discrete pins. When floating MODE,

there should be no external load on the pin. MODE defines the status of 13 pins (see Table 2).

PCS - Parallel Chip Select, Pin 18. (Extended Hardware Mode)

Setting PCS high causes the line interface to ignore the TCODE, RCODE, LEN0, LEN1, LEN2,

RLOOP, LLOOP and TAOS inputs.

RCODE - Receiver Decoder Select, Pin 17. (Extended Hardware Mode)

Setting RCODE low enables B8ZS or HDB3 zero substitution in the receiver decoder. Setting

RCODE high enables the AMI receiver decoder (see Table 8).

RLOOP - Remote Loopback, Pin 26. (Hardware and Extended Hardware Modes)

Setting RLOOP to a logic 1 causes the recovered clock and data to be sent through the jitter

attenuator (if active) and through the driver back to the line. The recovered signal is also sent to

RCLK and RPOS/RNEG (or RDATA). Any TAOS request is ignored. In the Host Mode,

simultaneous selection of RLOOP & TAOS enables a factory test mode.

Simultaneously taking RLOOP and LLOOP high for at least 200 ns initiates a device reset.

SCLK - Serial Clock, Pin 27. (Host Mode)

Clock used to read or write the serial port registers. SCLK can be either high or low when the line

interface is selected using the CS pin.

SDI - Serial Data Input, Pin 24. (Host Mode)

Data for the on-chip register. Sampled on the rising edge of SCLK.

SDO - Serial Data Output, Pin 25. (Host Mode)

Status and control information from the on-chip register. If CLKE is high SDO is valid on the

rising edge of SCLK. If CLKE is low SDO is valid on the falling edge of SCLK. This pin goes to

a high-impedance state when the serial port is being written to or after bit D7 is output.

CS61577

DS155F

21