VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
ATM/SONET/SDH 622/155Mb/s Transceiver
Mux/Demux with Integrated Clock Generation
VSC8116
PLL clock multiplier. Optics have either a PECL or TTL output, usually called “SD” (Signal Detect) or “FLAG”
indicating either a lack of or presence of optical power. Depending on the optics manufacture this signal is
either active high or active low polarity. If the optics Signal Detect or FLAG output is a “TTL” signal, it should
be connected to LOSTTL. If it’s a “PECL” signal it should be connected through a “PECL” to “TTL” translator
(such as the Motorola “MC100ELT21”) which then drives LOSTTL. The follow on part to VSC8116 is the
VSC8117, in this device the signal LOSTTL has been changed to LOSPECL, a PECL input.
Facility Loopback
The Facility Loopback function is controlled by the FACLOOP signal. When the FACLOOP signal is set
high, the Facility Loopback mode is activated and the high speed serial receive data (RXDATAIN) is presented
at the high speed transmit output (TXDATAOUT). See Figure 3. In Facility Loopback mode the high speed
receive data (RXDATAIN) is also converted to parallel data and presented at the low speed receive data output
pins (RXOUT [7:0]). The receive clock (RXCLKIN) is also divided down and presented at the low speed clock
output (RXLSCKOUT).
Figure 3: Facility Loopback Data Path
D
Q
D
Q
1:8
Serial to
Parallel
RXOUT[7:0]
RXDATAIN
÷8
RXLSCKOUT
TXIN[7:0]
RXCLKIN
1
0
Q
D
Q
D
8:1
TXDATAOUT
Parallel to
Serial
1
0
PLL
FACLOOP
Equipment Loopback
The Equipment Loopback function is controlled by the EQULOOP signal. When the EQULOOP signal is
set high, the Equipment Loopback mode is activated and the high speed transmit data generated from the paral-
lel to serial conversion of the low speed data (TXIN [7:0]) is selected and converted back to parallel data in the
receiver section and presented at the low speed parallel outputs (RXOUT [7:0]). See Figure 4. The internally
generated 155MHz/622MHz clock is used to generate the low speed receive clock output (RXLSCKOUT). In
Equipment Loopback mode the transmit data (TXIN [7:0]) is serialized and presented at the high speed output
(TXDATAOUT).
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VITESSE SEMICONDUCTOR CORPORATION
741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896
G52220-0, Rev 4.1
1/8/00
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
