Operation Modes; Block Level Functions; Classification Of Signals And Overloading; Static Signals (Control Inputs) - Xilinx RocketIO X User Manual

Block Level Functions

Operation Modes

Internally, there are four modes of operation within the PCS: 16 bit, 20 bit, 32 bit, and 40 bit.
The PCS fundamentally operates in either 2-byte mode, or 4-byte mode, with 2-byte mode
corresponding to 16- and 20-bit mode, and with 4-byte mode corresponding to 32- and 40-
bit mode. When in 2-byte mode, the external interface can either be one, two, or four bytes
wide. When in 4-byte mode, the external interface can either be 4 or 8 bytes wide. It is not
possible to have an internal 2-byte width and an 8-byte external interface. It is also not
possible to have an internal 4-byte interface, along with a 1-byte external interface. See
Table

Table 2-1: PCS Interface Choice

A general guide to use is that 2-byte mode should be used in the PCS when the serial speed
is below 5 Gb/s, and the 4-byte mode should be used when the serial speed is greater than
5 Gb/s. In 2-byte mode, the PCS processes 4-byte data every other byte. This is transparent
to the user, but skews between transceivers result in larger bit skews at the transmit
interface as compared to Virtex-II Pro transceivers. Any one of the three encoding schemes
(8B/10B and 64B/66B encode/decode, SONET, and generic data modes) can be used in
either 2- or 4-byte mode, with each block having a bypass ability.
For more information on setting the PCS mode, refer to the block functional definition of
the bus interface in this guide.
Block Level Functions

Classification of Signals and Overloading

This section describes the pertinent signals at the interface of the PCS and how to prioritize
them. For more information about a particular signal, refer to the I/O specification, or the
particular block function of interest.

Static Signals (Control Inputs)

The following static signals are inputs that control the internal and external mode of
operation in the PCS. Typically, these signals would be the first consideration after the
mode of operation has been selected:
•
•
•
•
RocketIO™ X Transceiver User Guide
UG035 (v1.5) November 22, 2004
2-1.
Speed
2.488 Gb/s
5 - 10.3125 Gb/s
RXDATAWIDTH[1:0]
RXINTDATAWIDTH[1:0]
TXDATAWIDTH[1:0]
TXINTDATAWIDTH[1:0]
www.xilinx.com
1-800-255-7778
2 Byte (internal mode)
recommended
do not use
4 Byte (internal mode)
do not use
recommended
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