Altera Quartus II Settings File - Manual (Page 663)

OUTPUT_ENABLE_GROUP
Assigns an output enable group number for the specified node. Turning on this option directs the Fitter to
view the specified nodes as an output enable group so as not to violate the requirements for the maximum
number of pins driving out of a VREF group when a voltage-referenced input pin or bidirectional pin is
present. For bidirectional pins, the Fitter determines all possible pins that may potentially drive out when
any bidirectional pin is driving in by looking at the output enable of all the bidirectional pins in the VREF
group. This behavior can result in the VREF group exceeding the maximum number of outputs and result
in a no fit. Turning on the 'Output Enable Group' option allows you to specify an output enable group for
specific pins, thus allowing you to specify which pins in the design are driving in and out at the same time.
The Fitter only considers pins as potential outputs when they are in separate output enable groups or
when they are not in an output enable group; by specifying an output enable group, you can lower the
total number of outputs in the VREF group when any pin is driving in. As a result, the Fitter does not
count all of the potential outputs of the bidirectional pins and the number of outputs in the VREF group
remains in the legal range. You should turn on this option when the Fitter cannot detect the output enable
group of the pins in the VREF group, for example when the output enables come from a state machine or
complex logic. For detailed information on the number of outputs supported by a VREF group, refer to
the data sheet for the device family, which is available from the Literature section of the Altera web site.
Type
Integer
Device Support
This setting can be used in projects targeting any Altera device family.
Notes
This assignment supports wildcards.
This assignment supports Fitter wildcards.
Syntax
set_instance_assignment -name OUTPUT_ENABLE_GROUP -to -entity name>
Example
set_instance_assignment -name OUTPUT_ENABLE_GROUP 2 -to output_pin[0]
set_instance_assignment -name OUTPUT_ENABLE_GROUP 2 -to output_pin[1]
MNL-Q21005
2015.05.04
OUTPUT_ENABLE_GROUP 663
Quartus Settings File Reference Manual Altera Corporation
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