Selectable I/O Standards in Cyclone II Devices
After applying the equation above, apply one of the equations in
Table 10–9, depending on the package type.
Table 10–9. Bidirectional Pad Limitation Formulas (Where VREF Inputs Exist)
Package Type
Formula
FineLine BGA
(Total number of bidirectional pads) ≤9 (per VCCIOand
ground pair)
QFP
(Total number of bidirectional pads) ≤5 (per VCCIOand
ground pair)
When at least one additional output exists but no voltage referenced
inputs exist, apply the appropriate formula from Table 10–10.
Table 10–10. Bidirectional Pad Limitation Formulas (Where VREF Outputs
Exist)
Package Type
Formula
FineLine BGA
(Total number of bidirectional pads) + (Total number of
additional output pads) – (Total number of pads from the
smallest group of pads controlled by an OE) ≤9 (per VCCIO
and ground pair)
QFP
(Total number of bidirectional pads) + (Total number of
additional output pads) – (Total number of pads from the
smallest group of pads controlled by an OE) ≤5 (per VCCIO
and ground pair)
When additional voltage referenced inputs and other outputs exist in the
same VREF bank, the bidirectional pad limitation must again
simultaneously adhere to the input and output limitations. As such, the
following rules apply:
Total number of bidirectional pads + total number of input pads ≤30
(15 on each side of your VREF pad) for Fineline BGA packages
Total number of bidirectional pads + total number of input pads ≤20
(10 on each side of your VREF pad) for QFP packages
Altera Corporation
February 2008
10–31
Cyclone II Device Handbook, Volume 1
ALTERA [ ALTERA CORPORATION ]
