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RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007
Chapter 2:
Digital Design Considerations
R
In the 8B/10B decoding configuration, RXCHARISK asserted High indicates the received
byte of data is a control (K) character. Otherwise, the received byte of data is a data
character. See
Appendix B, “8B/10B Valid Characters”
.
The RXRUNDISP port indicates the disparity of the received byte is either negative or
positive. RXRUNDISP asserted High indicates positive disparity. This is used in cases like
the
below. When CLK_COR_INSERT_IDLE_FLAG = TRUE,
RXRUNDISP is asserted to flag the presence of an inserted clock correction sequence.
In the bypassed configuration, RXCHARISK and RXRUNDISP are additional data bits for
the 10-, 20-, or 40-bit buses, similar to the configuration on the transmit side. RXCHARISK
[0:3] relates to bits 9, 19, 29, and 39, while RXRUNDISP pertains to bits 8, 18, 28, and 38 of
the data bus. See
RXDISPERR
RXDISPERR is a status port for the receiver that is byte-mapped to RXDATA. When a bit in
RXDISPERR is asserted High, it means that a disparity error has occurred in the received
data. This usually indicates data corruption (bit errors) or transmission of an invalid
control character. It can also occur in cases where normal disparity is not required, such as
in the
RXNOTINTABLE
RXNOTINTABLE is a status port for the receiver that is byte-mapped to RXDATA. When it
is asserted High, it means that the received data is not in the 8B/10B tables. This port is
only used when the 8B/10B decoder is enabled.
Vitesse Disparity Example
To support other protocols, the transceiver can affect the disparity mode of the serial data
transmitted. For example, Vitesse channel-to-channel alignment protocol sends out:
K28.5+ K28.5+ K28.5- K28.5-
or
K28.5- K28.5- K28.5+ K28.5+
instead of:
K28.5+ K28.5- K28.5+ K28.5-
or
K28.5- K28.5+ K28.5- K28.5+
The logic must assert TXCHARDISPVAL to cause the serial data to send out two negative
running disparity characters.
Note:
If bypassing 8B/10B encoding/decoding, the remaining 10 bits will be the 10-bit-encoded
version of the channel bonding sequence. This is the same as the clock correction sequence
shown in
Transmitting Vitesse Channel Bonding Sequence
TXBYPASS8B10B
| TXCHARISK
| | TXCHARDISPMODE
| | | TXCHARDISPVAL
| | | | TXDATA
| | | | |
0 1 0 0 10111100 K28.5+ (or K28.5-)
0 1 0 1 10111100 K28.5+ (or K28.5-)
0 1 0 0 10111100 K28.5- (or K28.5+)
0 1 0 1 10111100 K28.5- (or K28.5+)
Product Not Recommended for New Designs