GL9714 datasheet(30/46 Pages) GENESYS

30 / 46 page

GL9714 PCI Express

TM PIPE x4 PHY

Page 30

8B/10B Decode Error

When the GL9714 decodes the received 10-bit symbol and detects an error code which does not

correspond to any valid data, it will replace the code with an EDB symbol, assert PHYSTS and encode

RXSTSx[2:0] with the values of decode error status, 3’b100.

Elastic Buffer Overrun and Underrun

When the overrun or underrun of the elastic buffer occurs, the GL9714 will assert PHYSTS and encode

RXSTSx[2:0] with the values of decode error status.

Elastic Buffer

RXSTS Code

Overrun

101b

Underrun

110b

In the case of elastic buffer overrun, the GL9714 drops the symbol. For the elastic buffer underrun, the

GL9714 inserts the EDB symbol. The PHYSTS and RXSTSx[2:0] are presented on the MAC interface

during the clock cycle where GL9714 drops or inserts the symbol.

Disparity Errors

To report a disparity error detected, the GL9714 asserts PHYSTS and encodes RXSTSx[2:0] with the

values of decode error status, 3’b111.

6.5 Loopback

The GL9714 supports a Loopback mode to re-transmit its received data. When the MAC sets the GL9714 in P0

state and asserts TXDET/LPBK, the GL9714 enters a Loopback. In Loopback, the GL9714 transmits data from

it received data instead of MAC interface. Meanwhile, it presents the received data on the MAC interface as

normal operation.

When set into Loopback mode and acting as a Loopback slave according to the PCI Express Base Specification

Rev. 1.0a, the GL9714 received data from the Loopback master. If the master intends to end the Loopback, it

sends an electrical idle ordered-set to the GL9714. When the MAC detects the electrical idle ordered-set, it

de-asserts TXDET/LPBK and asserts TXIDLE to instruct the GL9714 to stop Loopback. The MAC should take

care the GL9714 has retransmit at least three bytes of the electrical idle before it makes the GL9714’s transmitter

into electrical idle.

6.6 Polarity Inversion

The GL9714 supports lane polarity inversion. While pin RXPLRx asserted, the GL9714 inverts its received data

on the MAC interface.

6.7 Setting Negative Disparity

To set the running disparity to negative, the MAC asserts TXCMPx for one PCLK cycle that matches with the

data that is to be transmitted where running disparity is negative.

GL9714 Datasheet(PDF) 30 Page - GENESYS LOGIC