EP4CE30F29C7N Datasheet, PDF (112/488 Pages) Altera Corporation – Cyclone IV Device Handbook, Volume 1

6–6
Chapter 6: I/O Features in Cyclone IV Devices
OCT Support
The IOE registers in each I/O block share the same source for the preset or clear
features. You can program preset or clear for each individual IOE, but you cannot use
both features simultaneously. 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 the active-low input of another device upon power-up. If one register in
an IOE uses a preset or clear signal, 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.
f For more information about the input and output pin delay settings, refer to the Area
and Timing Optimization chapter in volume 2 of the Quartus II Handbook.
PCI-Clamp Diode
Cyclone IV devices provide an optional PCI-clamp diode enabled input and output
for each I/O pin. Dual-purpose configuration pins support the diode in user mode if
the specific pins are not used as configuration pins for the selected configuration
scheme. For example, if you are using the active serial (AS) configuration scheme, you
cannot use the clamp diode on the ASDO and nCSO pins in user mode. Dedicated
configuration pins do not support the on-chip diode.
The PCI-clamp diode is available for the following I/O standards:
■ 3.3-V LVTTL
■ 3.3-V LVCMOS
■ 3.0-V LVTTL
■ 3.0-V LVCMOS
■ 2.5-V LVTTL/LVCMOS
■ PCI
■ PCI-X
If the input I/O standard is one of the listed standards, the PCI-clamp diode is
enabled by default in the Quartus II software.
OCT Support
Cyclone IV devices feature OCT to provide I/O impedance matching and termination
capabilities. OCT helps prevent reflections and maintain signal integrity while
minimizing the need for external resistors in high pin-count ball grid array (BGA)
packages. Cyclone IV devices provide I/O driver on-chip impedance matching and
R_S OCT for single-ended outputs and bidirectional pins.
1 When using R_S OCT, programmable current strength is not available.
There are two ways to implement OCT in Cyclone IV devices:
■ OCT with calibration
■ OCT without calibration
Cyclone IV Device Handbook,
Volume 1
May 2013 Altera Corporation