Chapter 2: MAX V Architecture
2–33
I/O Structure
Output Enable Signals
Each MAX V IOE output buffer supports output enable signals for tri-state control.
The output enable signal can originate from the GCLK[3..0]global signals or from the
MultiTrack interconnect. The MultiTrack interconnect routes output enable signals
and allows for a unique output enable for each output or bidirectional pin.
MAX V devices also provide a chip-wide output enable pin (DEV_OE) to control the
output enable for every output pin in the design. An option set before compilation in
the Quartus II software controls this pin. This chip-wide output enable uses its own
routing resources and does not use any of the four global resources. If this option is
turned on, all outputs on the chip operate normally when DEV_OEis asserted. When
the pin is deasserted, all outputs are tri-stated. If this option is turned off, the DEV_OE
pin is disabled when the device operates in user mode and is available as a user I/O
pin.
Programmable Drive Strength
The output buffer for each MAX V device I/O pin has two levels of programmable
drive strength control for each of the LVTTL and LVCMOS I/O standards.
Programmable drive strength provides system noise reduction control for high
performance I/O designs. Although a separate slew-rate control feature exists, using
the lower drive strength setting provides signal slew-rate control to reduce system
noise and signal overshoot without the large delay adder associated with the
slew-rate control feature. Table 2–7 lists the possible settings for the I/O standards
with drive strength control. The Quartus II software uses the maximum current
strength as the default setting. The PCI I/O standard is always set at 20 mA with no
alternate setting.
Table 2–7. Programmable Drive Strength (Note 1)
I/O Standard
3.3-V LVTTL
IOH/IOL Current Strength Setting (mA)
16
8
8
3.3-V LVCMOS
4
14
7
2.5-V LVTTL/LVCMOS
1.8-V LVTTL/LVCMOS
1.5-V LVCMOS
6
3
4
2
1.2-V LVCMOS
3
Note to Table 2–7:
(1) The IOH current strength numbers shown are for a condition of a VOUT = VOH minimum, where the VOH
minimum is specified by the I/O standard. The IOL current strength numbers shown are for a condition of a
VOUT = VOL maximum, where the VOL maximum is specified by the I/O standard. For 2.5-V LVTTL/LVCMOS,
the IOH condition is VOUT = 1.7 V and the IOL condition is VOUT = 0.7 V.
1
The programmable drive strength feature can be used simultaneously with the
slew-rate control feature.
December 2010 Altera Corporation
MAX V Device Handbook
ALTERA [ ALTERA CORPORATION ]
