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AR# 14888

Virtex-II Pro RocketIO - What is the size of the receive (RX) elastic buffer?


What is the size of the RX elastic buffer in Virtex-II Pro MGTs?


The buffer is 64 deep by 13 bits.

The 13 bits include each byte of data (either 8 bits or 10 bits, depending upon the data path size) plus a number of status bits.

The RX elastic buffer goes to half full upon initialization or reset (RXRESET = 1), which is illustrated in the figure below:

Figure 1
Figure 1

The overflow and underflow mark is set when the difference between the read pointer and the write pointer is 12 or less. These cases are illustrated in the figure below:

Figure 2
Figure 2

An overflow or underflow on the RX elastic buffer causes RXBUFSTATUS[1] to go High.

AR# 14888
Date 12/15/2012
Status Active
Type General Article