Altera UG-01080 Betriebsanweisung Seite 218

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11–4 Chapter 11: Deterministic Latency PHY IP Core
Achieving Deterministic Latency
Altera Transceiver PHY IP Core November 2012 Altera Corporation
User Guide
1 Systems that require multiple PLLs in a single transceiver block must use a
delay estimate FIFO to determine delay estimates and the required phase
adjustments.
Figure 11–3 illustrates the use of TX feedback and an external VCXO for clock jitter
cleanup. It shows the following three delay variables:
T1—The delay from user logic to FPGA pin. Quartus II software includes this
delay in its timing models.
T2—The delay from the FPGA pin, to the external PLL and back to the FPGA
reference clock pin. You must provide the value for this delay.
T3—Includes the latency from the FPGA pin to the CMU PLL, from the CMU PLL
to the TX Serializer, and the TX PCS datapath to the TX Phase Compensation FIFO
tx_clkout
pin. Quartus II software includes this delay in its timing models.
Figure 11–3. Using TX PLL Feedback to Align the TX Core Clock with the RX Core Clock
nh
TX Data
RX Data
T3
T2
T1
bitslipboundaryselect (from RX Word Aligner)
TX PMA
tx_dataout
DQ
DQ
Serializer
RX PMA
De-
serializer
CMU
PLL
VCXO
CDR
refclk
(from On- or
Off-Chip PLL)
<n>
8B/10B
rx_datain
RX PCS
TX PCS
Using TX PLL Feedback to Align the TX and RX Datapaths
PCB
tx_clkout
pll_ref_clk
tx_clkout feedback path
rx_clkout
8B/10B
Word
Aligner
Bit Slip
TX Phase Comp
FIFO - Register
Mode
RX Phase Comp
FIFO - Register
Mode
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