Cyclone Device Handbook, Volume 1
of the standard. Using minimum settings provides signal slew rate
control to reduce system noise and signal overshoot. Table 2–11 shows the
possible settings for the I/O standards with drive strength control.
Table 2–11. Programmable Drive Strength Note (1)
IOH/IOL Current Strength Setting (mA)
I/O Standard
LVTTL (3.3 V)
4
8
12
16
24(2)
2
LVCMOS (3.3 V)
LVTTL (2.5 V)
4
8
12(2)
2
8
12
16(2)
2
LVTTL (1.8 V)
8
12(2)
2
LVCMOS (1.5 V)
4
8(2)
Notes to Table 2–11:
(1) SSTL-3 class I and II, SSTL-2 class I and II, and 3.3-V PCI I/O Standards do not
support programmable drive strength.
(2) This is the default current strength setting in the Quartus II software.
Open-Drain Output
Cyclone devices provide an optional open-drain (equivalent to an open-
collector) output for each I/O pin. This open-drain output enables the
device to provide system-level control signals (e.g., interrupt and write-
enable signals) that can be asserted by any of several devices.
2–50
Preliminary
Altera Corporation
January 2007
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