I/O Structure
Table 2–6. Programmable Drive Strength Note (1) (Part 2 of 2)
I
OH/IOL Current Strength Setting (mA)
I/O Standard
1.5-V LVCMOS
4
2
Note to Table 2–6:
(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.
Slew-Rate Control
The output buffer for each MAX II device I/O pin has a programmable
output slew-rate control that can be configured for low noise or
high-speed performance. A faster slew rate provides high-speed
transitions for high-performance systems. However, these fast transitions
may introduce noise transients into the system. A slow slew rate reduces
system noise, but adds a nominal output delay to rising and falling edges.
The lower the voltage standard (for example, 1.8-V LVTTL) the larger the
output delay when slow slew is enabled. Each I/O pin has an individual
slew-rate control, allowing the designer to specify the slew rate on a
pin-by-pin basis. The slew-rate control affects both the rising and falling
edges.
Open-Drain Output
MAX II devices provide an optional open-drain (equivalent to
open-collector) output for each I/O pin. This open-drain output enables
the device to provide system-level control signals (for example, interrupt
and write enable signals) that can be asserted by any of several devices.
This output can also provide an additional wired-OR plane.
Programmable Ground Pins
Each unused I/O pin on MAX II devices can be used as an additional
ground pin. This programmable ground feature does not require the use
of the associated LEs in the device. In the Quartus II software, unused
pins can be set as programmable GND on a global default basis or they
can be individually assigned. Unused pins also have the option of being
set as tri-stated input pins.
2–38Core Version a.b.c variable
MAX II Device Handbook, Volume 1
Altera Corporation
March 2008
ALTERA [ ALTERA CORPORATION ]
