EP2S90F1020C4 Datasheet, PDF (85/238 Pages) Altera Corporation – Section I. Stratix II Device Family Data Sheet

Stratix II Architecture
The Stratix II device IOE includes programmable delays that can be
activated to ensure input IOE register-to-logic array register transfers,
input pin-to-logic array register transfers, or output IOE register-to-pin
transfers.
A path in which a pin directly drives a register may require the delay to
ensure zero hold time, whereas a path in which a pin drives a register
through combinational logic may not require the delay. Programmable
delays exist for decreasing input-pin-to-logic-array and IOE input
register delays. The Quartus II Compiler can program these delays to
automatically minimize setup time while providing a zero hold time.
Programmable delays can increase the register-to-pin delays for output
and/or output enable registers. Programmable delays are no longer
required to ensure zero hold times for logic array register-to-IOE register
transfers. The Quartus II Compiler can create the zero hold time for these
transfers. Table 2–13 shows the programmable delays for Stratix II
devices.
Table 2–13. Stratix II Programmable Delay Chain
Programmable Delays
Input pin to logic array delay
Input pin to input register delay
Output pin delay
Output enable register t_CO delay
Quartus II Logic Option
Input delay from pin to internal cells
Input delay from pin to input register
Delay from output register to output pin
Delay to output enable pin
The IOE registers in Stratix II devices share the same source for clear or
preset. You can program preset or clear for each individual IOE. You can
also program the registers to power up high or low after configuration is
complete. If programmed to power up low, an asynchronous clear can
control the registers. If programmed to power up high, an asynchronous
preset can control the registers. This feature prevents the inadvertent
activation of another device's active-low input upon power-up. If one
register in an IOE uses a preset or clear signal then all registers in the IOE
must use that same signal if they require preset or clear. Additionally, a
synchronous reset signal is available for the IOE registers.
Double Data Rate I/O Pins
Stratix II devices have six registers in the IOE, which support DDR
interfacing by clocking data on both positive and negative clock edges.
The IOEs in Stratix II devices support DDR inputs, DDR outputs, and
bidirectional DDR modes.
Altera Corporation
May 2007
2–77
Stratix II Device Handbook, Volume 1