VSC8140QR View Datasheet(PDF) - Vitesse Semiconductor

Part Name

Description

Manufacturer

VSC8140QR

2.48832Gb/s 16:1 SONET/SDH Transceiver with Integrated Clock Generator

Vitesse Semiconductor 

VITESSE

SEMICONDUCTOR CORPORATION

2.48832Gb/s 16:1 SONET/SDH

Transceiver with Integrated Clock Generator

Data Sheet

VSC8140

Figure 9: AC Termination of Low-Speed LVPECL RXOUT[15:0] Outputs

VSC8140

VCC

VEE

VCC

R1 = 125Ω

Zo

R2 = 83Ω

100nF

bias point

generated

externally VEE

R3 =83Ω

R4 = 125Ω

downstream

Parity

Systems employing internal parity are supported by the VSC8140. On the transmit side, a parity check is

performed between the TXPARITYIN input and the 16 TXIN[15:0] bits.

PARMODE is used to select even or odd parity expected for these 17 bits. (TXIN[15:0] and TXPARI-

TYIN). PARMODE = “0” selects odd, PARMODE = “1” selects even. The PARERR output (parity error out-

put) is asserted active high when the parity of the 17 bits (TXIN[15:0] and TXPARITYIN) does not conform to

the expected parity designated by PARMODE. PARERR becomes available TDV after the rising edge of

TXCLK16I. PARERR is a NRZ pulse that is updated every 6.4 ns, i.e., the period of TXCLK16I. The timing

relationship of PARERR to TXCLK16I is shown in Figure 17. The PARERR pin may be left open if parity is

unused.

On the receive side, the parity output (RXPARITYOUT) is simply the XOR of all 16 outputs.

Loss of Signal

The VSC8140 has a TTL input LOS to force the part into a Loss of Signal (LOS) state. Most optics have a

TTL output usually called Signal Detect (SD), based on the optical power of the incoming light stream.

Depending on the optics manufacturer, this signal is either active high or low. To accommodate polarity differ-

ences, the internal Loss of Signal is generated when the POL and LOS inputs are of opposite states. Once active,

all zeroes “0” will be propagated downstream using the transmit clock until the optical signal is regained and

LOS and POL are in the same logic state.

Page 6

© VITESSE SEMICONDUCTOR CORPORATION

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

G52251-0, Rev. 4.0

9/6/00

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