5–42
Altera Corporation
Stratix Device Handbook, Volume 2
July 2005
SERDES Bypass DDR Differential Signaling
Switching Characteristics
Timing specifications for Stratix devices are listed in
Tables 5–7 and
5–8.You can also find Stratix device timing information in the Stratix Device
Family Data Sheet section of the Stratix Device Handbook, Volume 1.
Timing Analysis
Differential timing analysis is based on skew between data and the clock
signals. For static timing analysis, the timing characteristics of the
differential I/O standards are guaranteed by design and depend on the
frequency at which they are operated. Use the values in the Stratix Device
Family Data Sheet section of the Stratix Device Handbook, Volume 1 to
calculate system timing margins for various I/O protocols. For detailed
descriptions and implementations of these protocols, see the Altera web
SERDES Bypass
DDR Differential
Signaling
Each Stratix device high-speed differential I/O channel can transmit or
receive data in by-two (
×2) mode at up to 624 Mbps using PLLs. These
pins do not require dedicated SERDES circuitry and they implement
serialization and deserialization with minimal logic.
SERDES Bypass DDR Differential Interface Review
Stratix devices use dedicated DDR circuitry to implement
×2 differential
signaling. Although SDR circuitry samples data only at the positive edge
of the clock, DDR captures data on both the rising and falling edges for
twice the transfer rate of SDR. Stratix device shift registers, internal global
PLLs, and I/O cells can perform serial-to-parallel conversions on
incoming data and parallel-to-serial conversion on outgoing data.
SERDES Clock Domains
The SERDES bypass differential signaling can use any of the many clock
domains available in Stratix devices. These clock domains fall into four
categories: global, regional, fast regional, and internally generated.
General-purpose PLLs generate the global clock domains. The fast PLLs
can generate additional global clocks domains. Each PLL features two
taps that directly drive two unique global clock networks. A dedicated
clock pin drives each general-purpose PLL. These clock lines are utilized
page 5–19, respectively, show the available clocks in Stratix devices.