Ports And Attributes; Txbuferr; Tx_Buffer_Use; Rxbufstatus - Xilinx RocketIO User Manual

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R

Ports and Attributes

TXBUFERR

When High, this port indicates that a transmit buffer underflow or overflow has occurred.
Once set High, TXRESET must be asserted to clear this bit.

TX_BUFFER_USE

This attribute allows the user to bypass the transmit buffer. A value of FALSE bypasses the
buffer, while a TRUE keeps the buffer in the data path. This attribute should always be set
to TRUE.

RXBUFSTATUS

This 2-bit port indicates the status of the receiver elastic buffer. RXBUFSTATUS[1] High
indicates if an overflow/underflow error has occurred. (Once set High, the assertion of
RXRESET or RXREALIGN clears this bit.) RXBUFSTATUS[0] High indicates that the elastic
buffer is at least half-full.

RX_BUFFER_USE

When set to FALSE, this attribute causes the receive buffer to be bypassed. It should
normally be set to TRUE, since channel bonding and clock correction use the receive buffer
for realignment. When the buffer is bypassed, the user logic must be clocked with
RXRECCLK.

Miscellaneous Signals

Ports and Attributes
Several ports and attributes of the MGT have very unique functionality. The following do
not have large roles in the other functionality discussed so far:
RX_DATA_WIDTH,

TX_DATA_WIDTH

These two attributes define the data width in bytes of RXDATA and TXDATA respectively.
The possible values of each attribute are 1, 2, and 4, which correspond to 8-, 16-, and 32-bit
data buses when 8B/10B encoding/decoding is used. (See
page
bypassed.

SERDES_10B

This attribute allows the MGT to expand its serial speed range. The normal operational
speed range of 1.0 Gb/s to 3.125 Gb/s (20 times the reference clock rate) is obtained when
this attribute is set to FALSE. When set to TRUE, the MGT serial data will run at 10 times
the reference clock rate, producing a speed range of 600 Mb/s to 1 Gb/s.
90
60.) The bus widths are 10, 20, and 40 bits when 8B/10B encoding/decoding is
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Chapter 2: Digital Design Considerations
"8B/10B Encoding/Decoding,"
RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007