DP83251 datasheet(59/96 Pages) NSC

59 / 96 page

60 Pin Descriptions (Continued)

SERIAL INTERFACE

The Serial Interface consists of IO signals used to connect the PLAYER device to the Physical Medium Dependent (PMD)

sublayer

The PLAYER device uses these signals to interface to a Fiber Optic Transmitter (FOTX) Fiber Optic Receiver (FOXR) Clock

Recovery Device (CRD device) and Clock Distribution Device (CDD device)

Symbol

Pin No

Description

Clock Detect

A TTL input signal from the Clock Recovery Device indicating that the

Receive Clock (RXCg) is properly synchronized with the Receive Data RXDg)

TTLSD

Signal Detect

A TTL signal from the clock Recovery Device indicating that a signal is

being received by the Fiber Optic Receiver

RXDa

Receive Data

Differential 100K ECL 125 Mbps serial data input signals from the Clock

Recovery Device

RXDb

TXDa

Transmit Data

Differential 100K ECL 125 Mbps serial data output signals to the Fiber

Optic Transmitter

TXDb

ELB

External Loopback Enable

A TTL output signal to the Clock Recovery Device which

enablesdisables loopback data through the Clock Recovery Device This signal is

controlled by the Mode Register

LBDa

Loopback Data

Differential 100K ECL 125 Mbps external serial loopback data output

signals to the Clock Recovery Device

LBDb

When the PLAYER device is not in external loopback mode the LBDa signal is kept

high and the LBDb signal is kept low

TEL

FOTX Enable Level

A TTL input signal to select the Fiber Optic Transmitter Enable

(TXE) signal level

TXE

FOTX Enable

A TTL output signal to enabledisable the Fiber Optic Transmitter The

output level of the TXE pin is determined by three parameters the Transmit Enable (TE)

bit in the Mode Register the TM2 – TM0 bits in the Current Transmit State Register and

also the input to the TEL pin

The following rules summarizes the output of the TXE pin

(1) If TE e 0 and TEL e GND then TXE e VCC

(2) If TE e 0 and TEL e VCC then TXE e GND

(3) If TE e 1 and OTM and TEL e GND then TXE e VCC

(4) If TE e 1 and OTM and TEL e VCC then TXE e GND

(5) If TE e 1 and not OTM and TEL e GND then TXE e GND

(6) If TE e 1 and not OTM and TEL e VCC then TXE e VCC

DP83251 Datasheet(PDF) 59 Page - National Semiconductor (TI)

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