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EP1S20F672C7N Datasheet, PDF (502/864 Pages) List of Unclassifed Manufacturers – Stratix Device Handbook, Volume 1 | |||
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Source-Synchronous Timing Budget
Source-
Synchronous
Timing Budget
â After the pattern detection state machine, use another synchronizing
register to capture the generated SYNC signal and synchronize it to
the Ã1 clock.
â Since the skew in the path from the output of this synchronizing
register to the PLL is undefined, the state machine must generate a
pulse that is high for two Ã1 clock periods.
â Since the SYNC generator circuitry only generates a single fast clock
period pulse for each SYNC pulse, you cannot generate additional
SYNC pulses until the comparator signal is reset low.
â To guarantee the pattern detection state machine does not incorrectly
generate multiple SYNC pulses to shift a single bit, the state machine
must hold the SYNC signal low for at least three Ã1 clock periods
between pulses.
This section discusses the timing budget, waveforms, and specifications
for source-synchronous signaling in Stratix devices. LVDS, LVPECL,
PCML, and HyperTransport I/O standards enable high-speed data
transmission. This high data-transmission rate results in better overall
system performance. To take advantage of fast system performance, you
must understand how to analyze timing for these high-speed signals.
Timing analysis for the differential block is different from traditional
synchronous timing analysis techniques.
Rather than focusing on clock-to-output and setup times, source-
synchronous timing analysis is based on the skew between the data and
the clock signals. High-speed differential data transmission requires you
to use timing parameters provided by IC vendors and to consider board
skew, cable skew, and clock jitter. This section defines the source-
synchronous differential data orientation timing parameters, and timing
budget definitions for Stratix devices, and explains how to use these
timing parameters to determine a design's maximum performance.
Differential Data Orientation
There is a set relationship between an external clock and the incoming
data. For operation at 840 Mbps and W = 10, the external clock is
multiplied by 10 and phase-aligned by the PLL to coincide with the
sampling window of each data bit. The third falling edge of high-
frequency clock is used to strobe the incoming high-speed data.
Therefore, the first two bits belong to the previous cycle. Figure 5â23
shows the data bit orientation of the Ã10 mode as defined in the
Quartus II software.
5â30
Stratix Device Handbook, Volume 2
Altera Corporation
July 2005
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