G52142-0, Rev 4.2

© VITESSE SEMICONDUCTOR CORPORATION

Page 3

8/31/98

741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896

VITESSE

SEMICONDUCTOR CORPORATION

Data Sheet

VSC8111

ATM/SONET/SDH 155/622 Mb/s Transceiver

Mux/Demux with Integrated Clock Generation

Receive Section

High speed Non-Return to Zero (NRZ) serial data at 155Mb/s or 622Mb/s are received by the RXDATAIN

inputs. RXDATAIN is clocked in on the rising edge of RXCLKIN+. See Figure 2. The serial data is converted to

byte-wide parallel data and presented on RXOUT[7:0] pins. A divide-by-8 version of the high-speed clock

(RXLSCKOUT) should be used to synchronize the byte-serial RXOUT[7:0] data with the receive portion of the

UNI device.

The receive section also includes frame detection and recovery circuitry which detects the SONET/SDH

frame, aligns the received serial data on byte boundaries, and initiates a frame pulse on FP coincident with the

byte aligned data. The frame recovery is initiated when OOF is held high which must occur at least 4 byte clock

cycles before the A1A2 boundary. The OOF input control is a level-sensitive signal, and the VSC8111 will con-

tinually perform frame detection and recovery as long as this pin is held high even if 1 or more frames has been

detected. Frame detection and recovery occurs when a series of three A1 bytes followed by three A2 bytes has

been detected. The parallel output data on RXOUT[7:0] will be byte aligned starting on the third A2 byte. When

a frame is detected, a single byte clock period long pulse is generated on FP which is synchronized with the

byte-aligned third A2 byte on RXOUT[7:0]. The frame detector sends an FP pulse only if OOF is high or if a

frame was detected while OOF was being pulled low.

Figure 2: Data and Clock Receive Block Diagram

Loss of Signal

During a LOS condition, the VSC8111 forces the receive data low which is an indication for any downstream

equipment that an optical interface failure has occurred. The receive section is clocked by the transmit section’s

DQ

DQ

DQ

0

1

Divide-by-8

CMU

DQ

PM5355

DQ

RXOUT[7:0]

FP

RXLSCKOUT

VSC8111

RXDATAIN+

RXDATAIN-

RXCLKIN+

RXCLKIN-

LOSPOL

LOSTTL

1:8 Serial

to Parallel