EP1AGX Datasheet, PDF (25/234 Pages) Altera Corporation – Section I. Arria GX Device Data Sheet

Chapter 2: Arria GX Architecture
2–19
Transceivers
8B/10B Decoder
The 8B/10B decoder is used in all supported functional modes. The 8B/10B decoder
takes in 10-bit data from the rate matcher and decodes it into 8-bit data + 1-bit control
identifier, thereby restoring the original transmitted data at the receiver. The 8B/10B
decoder indicates whether the received 10-bit character is a data or control code
through the rx_ctrldetect port. If the received 10-bit code group is a control
character (Kx.y), the rx_ctrldetect signal is driven high and if it is a data
character (Dx.y), the rx_ctrldetect signal is driven low.
Figure 2–17 shows a 10-bit code group decoded to an 8-bit data and a 1-bit control
indicator.
Figure 2–17. 10-Bit to 8-Bit Conversion
j hg f i e dc b a
9 87 65 4 3 21 0
MSB Received Last
8B/10B Conversion
LSB Received First
ctrl
7 6 5 4 3 2 1 0 Parallel Data
HG FE D CB A
If the received 10-bit code is not a part of valid Dx.y or Kx.y code groups, the 8B/10B
decoder block asserts an error flag on the rx_errdetect port. If the received 10-bit
code is detected with incorrect running disparity, the 8B/10B decoder block asserts an
error flag on the rx_disperr and rx_errdetect ports. The error flag signals
(rx_errdetect and rx_disperr) have the same data path delay from the 8B/10B
decoder to the PLD-transceiver interface as the bad code group.
Receiver State Machine
The receiver state machine operates in Basic, GIGE, PCI Express (PIPE), and XAUI
modes. In GIGE mode, the receiver state machine replaces invalid code groups with
K30.7. In XAUI mode, the receiver state machine translates the XAUI PCS code group
to the XAUI XGMII code group.
© December 2009 Altera Corporation
Arria GX Device Handbook, Volume 1