VSC7126 Datasheet, PDF (2/16 Pages) Vitesse Semiconductor Corporation – 1.0625 Gbits/sec Fibre Channel Transceiver

1.0625 Gbits/sec Fibre
Channel Transceiver
VITESSE
SEMICONDUCTOR CORPORATION
Datasheet
VSC7126
Functional Description
Clock Synthesizer:
The VSC7126 clock synthesizer multiplies the 53.125 MHz reference frequency provided on the TBC pin
by 20 to achieve a baud rate clock at nominally 1.0625 GHz. The clock synthesizer contains a fully monolithic
PLL which does not require any external components.
Serializer:
The VSC7126 accepts TTL input data as two parallel 10 bit characters on the T0:19 bus which is latched
into the input latch on the rising edge of TBC. This data will be serialized and transmitted on the TX PECL dif-
ferential outputs at a baud rate of twenty times the frequency of the TBC input, with bit T0 transmitted first.
User data should be encoded for transmission using the 8B/10B block code described in the Fibre Channel spec-
ification, or an equivalent, edge rich, DC-balanced code. If either EWRAP or TXEN# is HIGH the transmitter
will be disabled with TX+ HIGH and TX- LOW. If both EWRAP and TXEN# are LOW, the transmitter outputs
serialized data.
Transmission Character Interface
In Fibre Channel, an encoded byte is 10 bits and is referred to as a transmission character. The 20 bit inter-
face on the VSC7126 corresponds to two transmission characters. This mapping is illustrated in Figure 1.
Figure 1: Transmission Order and Mapping to Fibre Channel Character
Parallel Data Bits
8B/10B Bit Position
Valid Comma Position
11111111110000000000
98765432109876543210
j hgf i edcbaj hgf i edcba
1111100
Last Data Bit Transmitted
First Data Bit Transmitted
Clock Recovery:
The VSC7126 accepts differential high speed serial inputs on the RX+/RX- pins, (when EWRAP is LOW),
extracts the clock and retimes the data. The serial bit stream should be encoded to provide DC balance and lim-
ited run length by a Fibre Channel compatible 8B/10B transmitter or equivalent. The VSC7126 clock recovery
circuitry is completely monolithic and requires no external components. For proper operation, the baud rate of
the data stream to be recovered should be within 200 ppm of twenty times the TBC frequency. This allows
oscillators on either end of the link to be 53.125 MHz +/- 100ppm.
Deserializer:
The retimed serial bit stream is converted into two 10-bit parallel output characters. The VSC7126 provides
a TTL recovered clock, RBC(0) and its complement RBC(1), at one-twentieth of the serial baud rate. The
clocks are generated by dividing down the high-speed clock which is phase locked to the serial data. The serial
data is retimed by the internal high-speed clock, and deserialized. The resulting parallel data will be captured
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© VITESSE SEMICONDUCTOR CORPORATION
741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: [phone]
G52148-0, Rev. 4.3
3/4/99