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6–6
Chapter 6: I/O Features in Cyclone IV Devices
OCT Support
March 2016
Altera Corporation
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
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
Summary of Contents for Cyclone IV
Page 10: ...x Chapter Revision Dates Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Page 14: ...I 2 Section I Device Core Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Page 274: ...vi Contents Cyclone IV Device Handbook February 2015 Altera Corporation Volume 2...
Page 440: ...iv Contents Cyclone IV Device Handbook December 2016 Altera Corporation Volume 3...
Page 442: ...vi Chapter Revision Dates Cyclone IV Device Handbook December 2016 Altera Corporation Volume 3...
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