AM79761 datasheet(7/20 Pages) AMD

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Am79761

PRELIMINARY

PIN DESCRIPTION

TX+, TX-

Serial Transmit Data

PECL Output

These pins are the 1000BASE-X port differential driv-

ers which transmit the serial stream to the network.

These pins are connected to the copper or ﬁber optic

connectors.

When EWRAP is LOW, the pins assume normal oper-

ation. When HIGH, TX+ is logic HIGH and TX- is logic

LOW.

RX+, RX-

Serial Receive Data

PECL Input

These pins are the 1000BASE-X port differential re-

ceiver pair, receiving a serial stream of data from the

network. These pins are connected to the copper or

ﬁber optic connectors.

When EWRAP is LOW, the pins assume normal oper-

ation. The pins are internally biased.

TXD[0:9]

Transmit Data

TTL Input

The TXD[0:9] pin is a set of 10 data signals which are

driven from the Physical Coding Sublayer (PCS) above.

The 10 bits of data are clocked in parallel on the rising

edge of REFCLK. TXD0 is transmitted ﬁrst on TX

±.

RXD[0:9]

Receive Data

TTL Output

The RXD[0:9] pin is a set of 10 data signals which are

sent to the Physical Coding Sublayer (PCS) above. The

10 bits of data are clocked out in parallel on the rising

edges of RCLK and RCLKN. RXD0 is received ﬁrst on

±.

REFCLK

Reference Clock

TTL Input

This input is used for the 125-Mhz clock. The rising

edge of this clock latches TXD[0:9] into an input regis-

ter. This clock serves as the reference clock at 1/10th

the baud rate for the PLL.

RCLK, RCLKN

Receive Clock

TTL Output

These pins provide the differential receive clock sig-

nals, derived from the RX

± data stream, and are at

1/20th the baud rate of the receive stream. Parallel data

on RXD[0:9] is provided at each rising transition of

RCLK and RCLKN.

EN_CDET

Enable Comma Detect

TTL Input

This pin is used to enable the word synchronization

mode. When logic HIGH, the COM_DET output is en-

abled and word synchronization is active.

COM_DET

Comma Detect Indicator

TTL Output

Comma Detect is asserted to indicate that the incoming

word on RXD[0:9] contains a Comma character

(0011111xxx). COM_DET goes HIGH for half of a RCLK

period, and can be captured when RCKLN is rising.

In order for COM_DET to provide indication, EN_CDET

must be enabled (logic HIGH).

EWRAP

Loopback Enable

TTL Input

When EWRAP is asserted, the transmitted data stream

is sent back to the receiver through an internal loop-

back path. TX+ is logic HIGH, and TX- is logic LOW in

this mode.

This pin is logic LOW for normal operation.

TEST[1:3]

Factory Test Pins

Input

These pins should be tied to DVDD for normal operation.

TEST[4]

Factory Test Pin

Output

This pin should be left unconnected for normal operation.

DVDD

Power

These pins supply power to the digital blocks of the

device. They must be connected to a 3.3 V

±5% source.

DVDD_T

TTL Power

These pins supply power to the TTL blocks of the de-

vice. They must be connected to a 3.3 V

±5% source.

DVDD_P

PECL Power

These pins supply power to the PECL blocks of the de-

vice. They must be connected to a 3.3 V

±5% source. It

is critical that the signal supplied to these pins are

clean to ensure good performance of the device.

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