VITESSE

SEMICONDUCTOR CORPORATION

Advance Product Information

VSC7146

2.5Gb/s, 20-Bit Transceiver

Page 14

© VITESSE SEMICONDUCTOR CORPORATION

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

8/28/00

G52162-0 Rev. 2.7

Table 6: Pin Identifications

Pin #

Name

Description

2, 4, 6, 9, 11, 14, 16, 18, 20,

23, 3, 5, 8, 10, 12, 15, 17,

19, 22, 24

T[0:19]

INPUTS - TTL:

Transmit Data Bus, Bit 0 through Bit 19. 20-bit Transmit Character. Parallel data on

this bus is clocked in on the rising edge of TBC. The data bit corresponding to T0 is

transmitted first.

26

REF

INPUT - TTL:

Reference Clock. REF goes to the PLL/CMU circuitry and is multiplied 20 times

28

TBC

INPUT - TTL:

Transmit Byte Clock.

This rising edge of this clock latches T[0:19] into the input register and provides the

reference clock at 1/20th of the baud rate to the PLL.

74,75

TX+, TX-

OUTPUTS - Differential (AC-coupling recommended):

Transmitter Serial Outputs. These pins output the serialized transmit data when

EWRAP is LOW. When EWRAP is HIGH, TX+ is HIGH and TX- is LOW.

65, 63, 59, 57, 55, 52, 50,

48, 45, 43, 64, 62, 58, 56,

54, 51, 49, 47, 44, 42

R[0:19]

OUTPUTS - TTL:

Receive Data Bus, Bits 0 thru 19. 20-bit received character. Parallel data on this bus

can be sampled on the rising edge of RBC. R0 is the first bit received on RX+/RX-.

35

TXRATE

INPUT - TTL:

Transmitter Dual Rate Selector. LOW for half-speed operation (1.25Gb/s). HIGH for

full-speed operation (2.5 Gbps).

79

RXRATE

INPUT - TTL:

Receiver Dual Rate Selector. LOW for half-speed operation (1.25Gb/s). HIGH for

full-speed operation (2.5Gb/s).

29

BCMN

INPUT - TTL:

Backwards Compatibility Mode Selector. LOW to allow operation in previous ver-

sion compatibility (no separate rate controls for transmitter and receiver). HIGH to

allow operation with separate rate controls for transmitter and receiver.

36

EWRAP

INPUT - TTL:

Enable Internal WRAP Mode. LOW for Normal Operation. When HIGH, an internal

loopback path from the transmitter to the receiver is enabled, TX+ = HIGH and TX-

is LOW.

68, 67

RX+, RX-

INPUTS - Differential (AC-coupling recommended):

Receive Serial Inputs. The receiver inputs when EWRAP is LOW.

38, 39

RBC, RBCN

OUTPUT - TTL:

RX+/- data rate. The rising edge of RBC corresponds to a new word on R[0:19].

34

EN_CDET

INPUT - TTL: ENable Comma DETect. Enables COM_DET and word resynchroni-

zation when HIGH. When LOW, keeps current word alignment and disables

COM_DET.

37

COM_DET

OUTPUT - TTL:

COMma DETect. This output goes HIGH to indicate that R[0:6] contains a “comma”

character (‘0011111’). COM_DET can be sampled on the rising edge of RBC.