VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
VSC8116
ATM/SONET/SDH 622/155Mb/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. The corresponding clock is received by the RXCLKIN 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 synchro-
nize 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 VSC8116 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
VSC8116
D Q
RXOUT[7:0]
PM5355
D Q
1:8 Serial
LOSTTL
RXDATAIN+
RXDATAIN-
RXCLKIN+
RXCLKIN-
0
1
CMU
Divide-by-8
D Q
to Parallel
D Q
FP
D Q
RXLSCKOUT
Loss of Signal
During a LOS condition, the VSC8116 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
G52220-0, Rev 4.1
1/8/00
©
VITESSE
SEMICONDUCTOR CORPORATION
741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896
Page 3
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
