EP2SGX30CF780C5N Datasheet, PDF (36/316 Pages) Altera Corporation – Section I. Stratix II GX Device Data Sheet

Transceivers
asserted. All 8B/10B control signals, such as disparity error or control
detect, are pipelined with the data in the Stratix II GX receiver block and
are edge aligned with the data.
Figure 2–23 shows how the 20-bit code is decoded to the 16-bit data +
2-bit control indicator.
Figure 2–23. 20-Bit to 16-Bit Decoding Process
j¹ h¹ g¹ f¹ i¹ e¹ d¹ c¹ b¹ a¹ j
hg
f
i
e dc b a
19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
MSB
LSB
Cascaded 8B/10B Conversion
CTRL[1..0] 15 14 13 13 11 10 9 8 7 6 5 4 3 2 1 0 Parallel Data
H¹ G¹ F¹ E¹ D¹ C¹ B¹ A¹ H G F E D C B A
There are two optional error status ports available in the 8B/10B decoder,
rx_errdetect and rx_disperr. These status signals are aligned with
the code group in which the error occurred.
Receiver State Machine
The receiver state machine operates in Basic, GIGE, PCI Express, 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.
Byte Deserializer
The byte deserializer widens the transceiver data path before the FPGA
interface. This reduces the rate at which the received data needs to be
clocked at in the FPGA logic. The byte deserializer block is available in
both single- and double-width modes.
The byte deserializer converts the one- or two-byte interface into a
two- or four-byte-wide data path from the transceiver to the FPGA logic
(see Table 2–9). The FPGA interface has a limit of 250 MHz, so the byte
deserializer is needed to widen the bus width at the FPGA interface and
2–28
Stratix II GX Device Handbook, Volume 1
Altera Corporation
October 2007