differential pins assignment in Synplify fro altera device

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Ive got differential signal ALE (composed from ALE_P and ALE_N) like
in attached vhdl entity:

entity top is
      ALE_p, ALE_n  : IN     std_logic
end top;

Could anybody tell me how in synplify constraint (sdc) assign
differential pins to this signals for altera stratix 2 device?

Is such assignment valid for Synplify: define_attribute
altera_chip_pin_lc {{AA3 AA4}}
??? (lets assume that AA3 and AA4 are differential pair pins)

Re: differential pins assignment in Synplify fro altera device
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The easiest method is to change your entity declaration to be single-
ended, and then assign a differential I/O standard to the input.  You
can assign the I/O standard in the Synplify constraint (sdc) file (but
I don't recall the exact syntax), or in the Quartus assignment editor
GUI, or with a Quartus Tcl command.  So your entity declaration

entity top is
       ALE_p  : IN     std_logic
end top;

Use altera_chip_pin_lc to assign the positive input pin to wherever
you would like, and Quartus will automatically create and place the
negative pin in the appropriate (paired) I/O slot.

For Stratix III and Cyclone III there is an alternative method if you
prefer.  For those devices, you can instantiate a differential
primitive, and then assign the positive and negative pin to I/O
locations yourself.  This doesn't really provide extra flexibility vs.
the above approach though, since the (+ve, -ve) I/O pairs are
predefined, so once you assign either the positive or negative pin
location, there is no choice as to where to put the other one.

Vaughn Betz

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